Cycling is really a misnomer, and many people don't really understand the process, hence the many myths that surround it.
"Cycling" is just achieving a balance between the "filtration" bacteria and the "bio load" - all the living and decaying organic matter in the system. You CAN "cycle" the tank with no substrate, but it will then only be able to sustain a very small bio-load. It works like this: as with most living organisms, bacteria need three things to multiply:
- enough food (in our case the fish waste, decomposing organics in the tank, and the food we put into the tank to feed the fish, corals, etc.). Even is all the other criteria are met, they just won't increase in population if they don't have enough food - this is why we need to "feed" our systems with ammonia, "frot" decomposing things in uncured live rock, or fish pee (but the latter is cruel to the fish, and thus not advisable). If you do not have any of the aforementioned, you need to feed them with any other handy food source, such as the expensive shop-bought "mutis", skimmate from another tank, or just a simple piece of seafood that can decompose in the tank (I prefer to use frozen human food type shrimp or prawn)
- enough "housing" substrate, be that rock, sand, bio balls or even inside living sponges. The bacteria don't care if their substrate is rock or sand - what they do care about is to have enough SURFACE AREA to populate, and fine sand just happens to have a much larger surface area than rock.
- enough "air to breath", this being oxygen (for aerobic bacteria) or sulpher, methane, nitrate (the important one for us...) or whatever the anaerobic bacteria use for respiration
- and of course some dim lights and soft, romantic music to get Mrs. bacterium into the right mood
Now, where do the bacteria come from? If you're patient enough, you don't need to add ANY bacteria to your tank - they are in the air all around (and inside) us - (yes, "marine" bacteria can be found as far as 1000km or more inland...). Of course, they are bound to be very scarce (even lowly bacteria would prefer not to live in Gauteng
), and it is practical to add sources of "proper" filtration bacteria to our tanks. A very good source of this is, of course, live rock. Alternatively, you could add some cultures that you buy from your LFS (expensive), or you could just import them in the gut and body of the frozen shrimps or prawns I mentioned earlier (that's why I prefer to use this method to feed my cycling tank...).
Of course, if you have an existing tank, you could just rinse one of your rocks in the new tank, and then place it back into the old tank - that alone should dump a good deal of bacteria into the new one...
Hennie
