A word of warning: starting a marine tank cause a serious change in human behavioural patterns - looking dreamy eyed at your tank for hours on end; phoning your loved ones (or anyone!) in the middle of the night to tell them about a new polyp, worm, glowing thingy about 1mm long, ... which you have just discovered; not buying new clothes, furniture etc. because your tank REALLY needs that new light, filter, ROCK, etc.... Oh well, maybe you won't get hooked so badly.

Firstly, get some advice.

Most peoples main source of advice is the Local Fish Store (LFS). Petshops, LFS's, call them what you like, these shops all exist primarily to make money. If they do, they are successful, and the owners can live in comfort (or even grow rich ??). If they don't make money, they go bankrupt. They will always try to sell you the most expensive (often quite useless), items, preferably something which you will have to upgrade later (another sale for them...). And these are the good ones - the bad shops will also sell you incompatible livestock, or diseased fish, or even fish caught with poisons, knowing that they will die after a few days. They can then blame it on you (bad water quality, wrong filter..."you also need this UV steriliser to reduce disease..." and because you are not sure yourself, you inevitably buy more equipment (usually also useless). Get the picture..?? So BUYER BEWARE!
People on Internet discussion groups do not have any financial gain by what they recommend, and are usually impartial, but there is another problem lurking - Pride. "I use skimmer xxx, or pump zzz, this is the best, use it!" "Oh, I've kept 10 types of Angels, and 4 types of Damsels in a 50 gallon tank for the past 5 years, Its EASY - you can do it too..." or even worse, "Oh, I am very successful with keeping anemones. They are easy to keep, I've had 5 in the last year..."
Advice in books is usually outdated. Details on the animals and plants tend to stay relevant, but "technical" issues such as filters, skimming, lighting, etc. tend to change rapidly, as new equipment and techniques are developed. So, before you decide on anything technical, query what the books say!
Whilst gathering your information, you must THINK. Is it logical, does it agree with what other books say, or with the views of "experts"? You must also get as many recommendations as you can, and then try to decide what is right FOR YOUR PARTICULAR SITUATION. Even some of the most notable "experts" on the net, some even with PhD's, can't agree on "what is right" all the time. They do tend to agree on the basics, though, so if you get some "way off" advice, you should be wary.

 

It appears that a few of you just may have learned something from yesterdays drill. Well, maybe, but when I get a question from someone that doesn't even have live rock in his tank it makes me wonder. Sheesh, the guy must be a Marine or something.

Anyway today we're gonna talk about chemical warfare. A lot of you maybe don't know it but there are WMD at work in your tank and unless you take the proper actions they may cause massive casualties.

The worst ingredient in these toxic agents is nitrogen. Good old N2, you may remember it from science class when you weren't showing off your light saber to Mary Easidate sitting next to you.

Now nitrogen gas just sits around being inert. In your tank right now you have around 11 or 12 parts per million just doing nothing; like most of you newbies. . It is when it becomes incorporated into organic materials, like proteins, that problems arise.

I know, I know your saying another nitrogen cycle thing. Well listen up this time numbnuts cause as the Master Jedi says, " You can't make him drink, a horse to water you lead.".

Nitrogen, in the form of protein, enters our tank mainly disguised as food, which is probably against the Geneva Convention. Your fish eat it, your corals eat it, your inverts eat it and even the algae and bacteria eat it. Once they eat it, without going through that whole list again, they all excrete it. When they excrete it the nitrogen has been changed to ammonia compounds. This is a powerful WMD.

Fairly small amounts of it reek havoc on your tank's inhabitants. In the ocean ammonia concentration are next to nothing. In a closed system, like your tank, they can buildup in the blink of an eye unless we have a means to de-detoxify the ammonia.

Now some of you may have seen Episode II, "Battle of the Seaclones" In it, the forces of protein fractionation, sometimes know as Skimmers, defeat the powerful Proteinions before they can morf into more deadly Ammoniums. A protein skimmer works just like beating egg whites, a protein, into a foam. By doing so you remove the protein before it converts to ammonia. I guess the the Axis powers were the first to propose this as they call it the Berlin Method.

There is a small problem with just relying on skimmers. For one, they are not 100% efficient and secondly, the tank inhabitants "gotta eat". Some protein will slip by and be converted to ammonia. In a fresh water system this is OK if it doesn't get out of hand. FW tanks are at pH's of 7 or lower, for the most part, and ammonia is not as toxic at low pH. With SW tanks, at pH around 8.3 the ammonia is much more toxic and tank inhabitants are less acclimated to even low levels. Small amounts can be deadly.

Even though the ammonia is less toxic in FW, the early colonialists were seeing losses from ammonia in their tanks. To combat this they declared biological warfare on ammonia.

There are bacteria (Nitrosomonas and Nitrococcus for those that get their jollies off things named with dead languages) that can convert ammonia to less toxic nitrite. Another group (Nitrobacter and Nitrosospira) can convert nitrite to nitrate that is even less toxic. There was a problem however. These bacteria are slow to develop, which, reminds me of you rookies.

The FW people took their cue from the doo-doo farmers of the wastewater planet of Polboe. The nitrifying bacteria attach themselves to objects and hold on for dear life, much like the slime worms of Polboe. They also require a ton of oxygen to survive. The answer was the underground filter or UGF. The sand provided the perfect environment for the bacteria to attach and the high flow through the sand insured adequate oxygen. It worked like a charm, allowing higher numbers of fish to be maintained in the same volume of water.

As a note to you Padawan learners-- this high use of oxygen can be a problem in a nitrifying, small tank or nano reef that doesn't have a sump or skimmer. I know you marines out there get away with it because you have a Diver Dan in your tanks connected to an air pump.

Well we covered quite a bit today. We'll finish this up tomorrow.

Yeah it's about time for some test kits but before I get into that, here is an article by Jedi candidate SAT. He covers many of the questions asked in his Jedi thesis RO/DI FAQ. I helped by giving him the line, "size does matter", although I can't remember if it was RO/DI that we were talking about.

It is good reading and packed full of good poop.

Imagine, SAT almost turned to the Darkside. Awhile back, we sensed great fear in SAT and found he was dosing multi-purpose additives. Can you imagine, without even testing to see if his tank was low on what he was adding. As the ancient Jedi proverb goes; "Additives you add, then test you must."

Dosing is just one reason to run tests on your tank. As a Newbie, you want to check the state of your cycle by ammonia testing. When your tank is established, tests can give you a handle on the overall health of your tank. When you have a problem testing can tell you; what has changed?

The good part is you don't need to be one of those smart-@ss CHEMISTRY GEEKS that have been known to lurk on this board and dispense their evil, non-decipherable malarkey. . Well, we do allow Doc Randy but he, as you know, is a droid.

As a hobbyist, you basically have three classes of tests you can run. The first is volumetric, where you add a solution that reacts with the substance you wish to find. Examples are the alkalinity test and calcium. The second is a colorimetric test where the substances sort after react with a dye. The intensity of the color tells you how much there is. Ammonia, nitrite and nitrate tests are all examples of colorimetric tests. Lastly we have instrumental methods where an instrument gives you a direct reading of the quantity of the unknown. Examples are TDS, pH and salinity. There are literally dozens of test kits you can buy but all of them can be grouped into these three basic classes. Let's take a closer look at each class and a few of the most commonly used tests in that class.

Volumetric kits rely on a technique know as titration. A solution of known concentration is mixed with a water sample that contains an unknown. An indicator is added that, when the reaction between the known solution and the unknown in the sample is complete, produces a color change.

The most common, and one of the most important for a person with a new tank, is alkalinity. Alkalinity is the ability of your tank to resist a change in pH. A tank with low alkalinity will be subject to much wider pH swings than a tank with higher alkalinity. The actual chemicals that make up alkalinity are hydroxides (strong bases), carbonates (mid-range bases) and bicarbonates (weak bases). Borates also are included in this group but we'll kind of ignore them to keep things simple.

HOLD IT RIGHT THERE!!! I see some of you heading for the door. NOBODY said it was easy to be a REEFER! HECK, if it was easy EVERYONE would have a reef tank.

As your tank becomes established alkalinity tends to become somewhat self-adjusting. On a new tank it can be a major concern. That is because the biological processes in your tank are in a growth phase. Remember what I said when we talked about nitrification; Nitrification EATS alkalinity. In a new tank it is not unusual to need to add a supplement to increase alkalinity.

The only way to know if we are low in alkalinity is to test for it. That is accomplished by using test kit. The alkalinity kit is one of the simplest. It usually has a solution of known concentration, called the titrant, an indicator and a measuring device to collect the correct sample size. In a lab the titrant is placed in a buret. This is a long, graduated tube that is marked, usually in milliliter. In test kits you usually get a dropping bottle, or srynge in place of the buret. You collect the proper size sample, add indicator then add the dropping solution drop by drop until the sample changes to the proper color, called an endpoint. By counting up the drops you used you just multiply by a conversion factor and, presto, you have the alkalinity.

Wait a dog-gone minute! DID I SEE YOU YAWN OVER THERE??? What's the matter? You and your girlfriend stay up all night watching the POD races in your tank? Drop and give me 20 kilojoules! Anyway-

The solution in the dropping bottle is usually a very weak solution of sulfuric acid. Don't worry I REALLY mean WEAK. The indicator used will vary by kit manufacturer. Methyl Orange was the original indicator used. It changes from an orange to a reddish hue at the endpoint. Some people have trouble detecting this color change. A mixed indicator, Bromcresol Green-Methyl Red, is often used as a replacement. It changes from an aquamarine to a pink color at the endpoint. The color change is not as exact as that produced by methyl orange. If you have a pH meter, and are unsure of the endpoint, you can check the pH at what you think is the correct number of drops. It should be pH 4.5 0.2. If you don't have a pH meter, then get some RO/DI water and add a little indicator. Now put in a drop of the titrating solution. The color should change immediately and this is the color you want.

If you have the bromcrecol green type indicator and it is in solution be mindful , my young Padawans, that it has a somewhat limited shelf life. If you are getting strange colors at the endpoint it is probably the indicator. Also, when you stir the sample do it gently. Carbon dioxide can be adsorbed from the air if you stir vigorously causing low results. Samples with very low alkalinity, below 50 ppm, are difficult to test accurately and results will be low. Hopefully, that won't matter as when the alkalinity is that low you are going to adjust it anyway.

Before we move on there is one other little detail. Above I used parts per million. Actually, I meant parts per million as calcium carbonate. Why? Because that is the unit we use in environmental labs. Your test kit may use other units so be sure you know what unit you are using when asking for help, as I know you will , on this board . Common units are milligrams per liter mg/l ( same as ppm) , milliequivalents per liter, meq/l and , German alkalinity units, dKH. It is easy to confuse meq/l and dKH as their ranges overlap. We can end up telling you your alkalinity is on the low side when it is normal because we thought you meant dKH and you gave us meg/l. RC provides a calculator to ease the transition from one unit to another-Unit Calculator. In general, us REAL chemists use ppm or mg/l (they're the same), the Expert Droids like meq/l and the Axis powers go by dKH.

What? OK, you can go to the latrine. I know this is getting kinda long but I want to wrap up volumetric analysis today before you take a break.

The other popular, and useful, volumetric kit is Calcium. The titrant here is EDTA (ethylenediamine tetraacetic acid, as I am sure you were wondering), an indicator specific for calcim (you don't even want to ask its name ) and in this case a buffer solution(s) (sodium hydroxide). The latter may be a separate solution or combined with the indicator in dry powder formulations. A word about dry powders. IMO it is best to use kits that use powders as opposed to solutions. The key here is shelf life. Very often these test kits sit around before shipment. Many liquid reagents deteriorate over time. Dry reagents are usually more stable and normally can be stored for at least a year.

Returning to the calcium test. It works just like the alkalinity titration. A buffer is added to increase the pH and to precipitate magnesium which could interfere. Cloudiness in the sample is normal after the buffer addition and does not hurt the outcome. The titrant is added again drop wise. The indicator changes from pink to purple to sky blue which signals the endpoint. It is the "pure" blue that gets people confused. This test has what is known in the trade as a "fugitive" endpoint. That is you get to what you think is true blue but a second latter it appears purple again. You add a drop or two and it looks good but again it changes back to purple. This can occur over and over again and drive you nuts! This is because EDTA is a powerful reagent when it comes to putting calcium into solution. It is used in those products your mommy dear sprays on the shower stall to keep the film, which comes from your dirty newbie bode, off the shower wall. In the test it tends to dissolve colloidal calcium carbonate in the sample and bring it into solution. This results in the indicator keeps going back to a purple color. When it first turns pure blue STOP, that is the endpoint. To check on the blue you want, again, add all the reagents to some RO/DI water and a drop or so of titrant. As the Jedi master says, "The blue you see is what you seek." One last word on calcium; once you start the test don't delay. The buffer system may precipitate calcium at the pH involved and give low results if you don't finish the analysis immediately.
 

What is RO/DI?

RO/DI stands for Reverse Osmosis and Deionization. The product is a multi-stage water filter, which takes ordinary tap water in and produces highly purified water.

Why do I need it?

Tap water often contains impurities that can cause problems when added to an aquarium. These may include phosphates, nitrates, chlorine, and various heavy metals. Phosphates and nitrates can cause algae blooms. Copper is often present in tap water due to leaching from pipes and is highly toxic to invertebrates. A RO/DI filter removes practically all of these impurities.


How does it work?

There are typically four stages in an RO/DI filter: sediment filter, carbon block, reverse osmosis membrane, and deionization resin. If there are less than four stages, something was left out (typically the DI stage). If there are more, something was duplicated.

The sediment filter, typically a foam block, removes particles from the water. Its purpose is to prevent clogging of the carbon block and RO membrane. Good sediment filters will remove particles down to one micron or smaller.

The carbon, typically a block of powdered activated carbon, filters out smaller particles (often down to 1/2 micron or smaller), adsorbs some dissolved compounds, and deactivates chlorine. The latter is the most important part: free chlorine in the water will destroy the RO membrane.

The RO membrane is a semi-permeable thin film. Water is forced through it under pressure. Molecules which are larger/heavier than water (which is very small/light) penetrate the membrane less easily and tend to be left behind.

The DI resin exchanges the remaining ions, removing them from the solution.


What are CTA, TFC, and PVC?

There are three types of RO membranes on the market: Cellulose Triacetate (CTA), Thin Film Composite (TFC), and Poly-Vinyl Chloride (PVC). Almost all of the membranes sold for aquarium use in the US are TFC. PVC membranes are currently available only outside the US. The notable difference between these types is how they are affected by chlorine: CTA membranes require chlorine in the water to prevent them from rotting. TFC membranes are damaged by chlorine and must be protected from it. PVC membranes are impervious to both chlorine and bacteria. This FAQ assumes you're buying a TFC membrane.

Do I need a DI stage?

You can save some money by purchasing a three-stage filter lacking the DI stage. Reverse osmosis typically removes 90-98% of all the impurities of note. If that is good enough for your purposes, then the DI stage is not necessary. RO filtration by itself is certainly better than plain tap water and in many cases is perfectly adequate.

RO filtration by itself is not adequate if your tap water contains undesirable elements that need to be reduced by more than 90-98%. For example, if there is 10 PPM of phosphates in your tap water, reducing it by 90% takes it to 1 PPM, which is still too high.

To save money up front, a DI stage can be easily added to the system at a later date.

 

After handling (literally) tons of the stuff (and doing many things wrong along the way), I thought I might take a few moments to write a wordy post on the subject of Live Rock.

Live Rock is the foundation of our reefs, and is where the most significant biological filtration takes place in our tanks. Toxic nitrates and nitrites are processed deep within the rock by many forms of bacteria. Good quality Live Rock will come with more than just bacteria, however. Good rock will be populated with corals, worms, pods, foraminiferans, and many other interesting creatures. Various macroalgaes, snails, crabs, and other inverts often "hitchhike" their way in on the rock also. A few undesirable hitchhikers such as pest anemones, hairy rock crabs, mantis shrimp, and more may also come with the rock- although a 15- minute soaking in high-salinity water (1.030 SG) will run many of these out.

Here are some of the most common types of Live Rock with descriptions (IMO & IME!):

1) Fiji- This is the most commonly available live rock on the market. It is very porous, providing good biological filtration and a lot of rock for the money. (Because it is not very dense!) Fiji rock is also usually rather inexpensive, although the quality varies a LOT from one vendor to the next. (wholesalers included.) Premium Fiji is quite beautiful once cured and encrusted with the purple coralline algae this rock is known for- but if you order the cheapest online Fiji, don't expect much!

2) Tonga Branch- Extremely dense, branched coral skeletons that add a very nice look and natural appearance to a mixed reef structure. It can be very heavy and usually carries less "life" than most types of LR. I like small amount of Tonga Branch for a diverse appearance, but do not use it as the only rock in a tank.

3) Kaileni- WOW! Deep-water Tonga rock that has a wide range of shapes, sizes, and densities. Some Tonga branch-like rock is usually mixed in small amounts, but most pieces are the huge caves and arches that make aquascapers drool. Many foraminiferans, fire corals, and a wide range of wildlife is found throughout the rock. Some of it is porous like Fiji, other pieces are hard, flat shelves or branches. This is my personal favorite Live Rock. The rock was originally named after importer Walt Smith's daughter- pronounced in the tongue of the people who collected the rock. Just a tidbit of LR trivia for ya.....

4) Caribbean- Very cool shelves and big, flat branchy pieces. Has a lot of the characteristics of Tonga branch, but not as dense. The Caribbean rock I have handled has been Haitian(I think), and is absolutely FULL of worms. Spaghetti worms, bristle worms, featherdusters- I don't know why, but there are always dozens of worms in the bag the rock comes in- so I dump them in the Live Sand vats, hehe.

5) Aquacultured rock- There are also many types of "Aquacultured" rock out there that are either man-made or mined rocks that have been kept in the ocean until colonized by marine life. Most of the man-made rock is a mixture of concrete, shells, and aragonite. Mined rock is usually aragonite or Limestone base rock. The aquacultured rock varies greatly in quality and appearance, depending on who is doing the culturing! Depending on where it is cultured, some of this rock may also be more likely to carry unwanted rock crabs and mantis shrimp. Tampa Bay Saltwater and Gulf-View are two companies that have a reputation for providing very high quality aquacultured rock. I have also seen some really bad examples out there- so be sure you are dealing with a reputable company if you are purchasing "Aquacultured" rock!

6) Misc.- There are many other varieties out there that can be hard to pin down. Buna spiny branch is a very nice looking rock that looks to be some kind of ancient acropora skeleton. Marshall Islands rock is very high quality, but is imported in smaller quantities, and is more expensive. I have also seen other Deep-Water Tonga rock that appears to be very similar to the Kaileni- perhaps just coming in through different importer channels.

Personally, I like to mix types of rock. It is my opinion that the wide variety of shapes and sizes looks more natural, and also should provide greater biodiversity from a wider range of fauna from different locations. Several of the types I have listed have specific advantages, and I like to mix the flat shelves of the Caribbean with the Kaileni Caves and Fiji boulders, with a few branches thrown in for something different.

About "Curing"...

Fresh Live rock must be "cured" before adding it to an existing system, basically because there are many dead things in there that did not survive the journey. "Curing" simply means waiting for the dying stuff to die, rot, or be eaten- while in a separate system that will not be damaged by the ammonia spike created by the funky stuff.

I think the most common mistake is not having enough water volume to cure the rock properly. If you pack 150+ lbs. of rock in a 45-gallon rubbermaid (like I did!) you will create a noxious stew that will kill many of the small organisms off that may have survived. (And, your spouse will talk about that reek coming from the basement for YEARS afterwards! ) Get the rock in as much volume as you can, such as a kiddie pool (perfect!) or large Rubbermaid trash can. You need as much circulation as you can get in there- drop a big pump in to churn the water if you can. Keeping the temperature high (80-82 degrees or so) will speed up the decay process and move things along. This is another common mistake: if the water is too cool, it sort of "preserves" the dead stuff, then it rots later- when you put it in your nice, warm tank! Hermits or snails can also help clean the rock up, but snails can only take so much of the ammonia. Frequent water changes are very helpful, especially during the first week- this is also when the smell reaches its peak. Sponges or other things that are rotting should be removed and the rock should be turned over/ blasted with a powerhead or lightly brushed with a soft-bristled brush to remove nasty stuff. I don't like scrubbing, because you remove a lot of worms and things that you might want to keep! I run actinic lighting over the rock as it is curing when possible, and reduce the photoperiod to a few hours a day. (Algae will descend on you if you give it too much light with all that goop in the water!)

After 3-4 weeks of this, the rock should be fully cured. I use my nose to tell me when it is ready, although I am told that test kits work also.

...If it smells like dead fish, put it back. If it smells like a jetty at low tide, it is ready. Be careful- sniffing LiveRock may kill brain cells-- or at least that would explain a lot after the tonnage I have sniffed!

For those of you who enjoy your kits, we are looking for the time when ammonia, nitrate, and nitrate levels are zero (or close to zero).

I do not consider myself an expert (are there any?), but I do know a lot of things I have done wrong when handling Live Rock in the past. If there is anything I can help with concerning the curing or handling or Live Rock (or anything else), please email, post, or message me- I will be glad to share any of my mistakes and experiences.
 

Mud! Why should you put Mud, of all things, in a coral reef aquarium? Well, the simple answer is that that mud will help create an environment that will almost force your corals and other decorative animals to thrive. With some 35 years of experience as a marine ecologist behind me, I can say that THE most important component of a coral reef aquarium is a deep sand bed, comprised of very fine sandy sediments that we can, without any hesitation, call MUD. In this article, I will discuss three things, first, the benefits of a sand bed, then how to set a bed up and, finally, some of the possible problems that you might encounter.

Benefits:

Hobbyists might think that sand beds have no place in a coral reef aquarium, particularly if they are trying to establish something resembling a natural coral reef. However, with some thought I am sure they would realize that most coral reefs are surrounded by sand area, and by constructing a sand bed in our aquariums we merely emulate nature. These beds provide three things. First, they provide a place for processing and exporting some dissolved nutrients. Second, they provide a place to recycle detritus, excess foods, animal feces and other particulate material into useable forms. Finally, they provide a food source for many reef animals. Let's look at each of these functions.

As they do in nature, the sand grain surfaces of sand beds in our systems provide the major substrate for nutrient-processing bacteria. The bacterial population is determined by three factors: the total sand surface area; the amount of nutrient available; and the number and effects of bacterial predators. All of these play a role in the development of the sand bed biological filter.

In a given volume of sand, the usable bacterial surface area rises rapidly as the average particle size decreases. For example, a cubical particle 1 mm on a side has 6 square mm of surface area, while the surface area on a particle that is one eighth (or 0.125) mm on a side is a total of 0.09375 square mm. However, in the volume of 1 cubic mm, there would be 512 of the smaller particles, for a total area of 48 square mm, eight times what is found on the larger cube.

The total sediment surface area in even a small tank is impressive, indeed. In my 45 gallon reef tank, the sand bed averages about 4 inches deep, by 12 inches wide, by 36 inches long, for a total of one cubic ft of sediment. I won't bore you with the calculations, but if the average particle size is one eighth mm, and that is a good average size to have, the total sand surface area is about 14,828 square feet or just slightly over 1/3 of an acre. A LOT of bacteria can live with that amount of space!

Although we seldom consider bacteria when we set up our systems, they are exceptionally important to the survival of every decorative fish or coral we add to the tank. Those bacteria are the biological filter of your reef tank, and by their simple existence and growth they detoxify and remove many of the excess nutrients from the system.

One organism's poison is another's nutrient. Fish and invertebrate urine, largely ammonium hydroxide, or ammonia gas dissolved in water, is the primary byproduct of necessary protein metabolism. Ammonia gas, even very small amounts dissolved in water, is highly toxic to animals. Likewise, phosphates are also byproducts of animal metabolism, and although not toxic to most animals, high phosphate concentrations may reduce or stop coral growth. The removal of both nitrogenous wastes, such as ammonia, and phosphates is accomplished by bacteria and microalgae which absorb these toxic animal byproducts and use them in their growth as necessary, required, and vital nutrients.

The surface area for bacteria and microalgae in live rock or on other surfaces is insignificant compared to the area in a sand bed four or more inches in depth. The cardinal rule of animal husbandry is that you have to feed animals, and many reef animals need to eat a lot. My article in the February 2001 Aquarium Fish Magazine (online version available: here) about the composition of many foods and additives can be used to calculate just how much of the various nutrients you add to your system. As an average the dried foods that I tested had about one half of their weight as protein, which in turn means they have a very large amount of phosphate in them. And, if that was not enough, once the food has been eaten and processed by the animals, they urinate out protein byproducts as ammonia. Simply feeding your fish or corals the necessary food they need to live may boost ammonia and phosphate concentrations several hundred to several thousand times what is normally found in reef water. But, if you have a deep sand bed, a process that is nothing short of miraculous occurs. The bacteria and algae living in the sediments take up the nutrients so fast and so thoroughly, that hobbyist test kits typically may not measure any of the nutrients at all even immediately after feeding.

These nutrients act as food for the bacteria. In a very real sense, the biological filter depends upon bacterial growth. The breakdown of nitrogen compounds to nitrogen gas is done by bacteria growing in the areas of lowered oxygen concentration in the deeper parts of the sediments. At normal reef temperatures, around 82 deg F, some bacterial species will double their population in less than a half hour if they have the appropriate nutrients. This rapid bacterial growth rate causes the release of nitrogen gas which becomes visible as bubbles in the sediments.