Fish, The Nitrogen Cycle, and Patience

When learning to keep an aquarium, the nitrogen cycle is the first thing people have to learn. If not, they usually learn it quickly when they take their dead fish back to their LFS. "I set up my 20 gallon tank last night and put 20lbs of uncured live rock, 10 clownfish and an anemone in it... what happened?"

 Basically, the nitrogen cycle is the process of breaking down waste. Fish excrement, left over food, dead plants, and even corals, hermit crabs, and snails excrete some form of waste. As this waste breaks down, it turns into Ammonia, which is highly toxic to fish. This ammonia becomes food for nitrifying bacteria, which break it down into Nitrite, which is also highly toxic to aquatic life. More nitrifying bacteria break down this nitrite into less toxic nitrate. Most fish can handle a fair ammount of nitrates (up to 30 mg/L), but for a reef aquarium, the concentration should be kept below 10 mg/L.

In an established aquarium, there are sufficient concentrations of nitrifying bacteria to break down all the waste as it is produced. That means there is virtually no detectable ammount of ammonia or nitrite in the system. However, in a new aquarium that bacteria (which is usually present on live rock or introduced by just about anything that has come from the ocean or an established tank) needs to be given time to establish itself in the tank in sufficient numbers so that it can deal with the waste produced when fish are added. This is the process of cycling a tank.

It is important to note here that this will not happen unless there is something in the aquarium for the bacteria to decompose. In freshwater tanks, this is usually the introduction of one or two hardy fish which will survive the toxic conditions. In a reef aquarium, however, this is best done with the introduction of snails and hermit crabs, uncured live rock (with decomposing algae or other organisms that did not survive the trip), or the addition of a few pieces of dead, uncooked shrimp.

So, back to our newbie with the dead livestock. He added way to many fish and invertibrates, so that the waste produced by the fish, anemone, and decomposing live rock built up to toxic conditions overnight, killing all his livestock. There was just not enough bacteria to keep up with the demand.

So, it is easy if you are patient. Add a small bioload to your tank and wait a month for the bacteria to establish, testing for ammonia, nitrite, and nitrate every few days. When the Ammonia and nitrite are no longer detectable, you can safely add fish.

I have a problems though - I am not patient. It has been just over two weeks now since setting up my aquarium, and I'm getting ancy to get something in it. Usually I would wait a month or so for the tank to finish cycling, but I'm not so sure it even went through a cycle period. Almost half of my live rock has been in a 15 gallon (containing two hermit crabs and a nocternal anemone) that has been set up since we moved here. It should have a significant amount of nitrifying bacteria establish already. The other half has been "cooking" in a dark tote for the last 9 months to rid it of hair algae. So... would the cycled live rock balance out the addition of the cooked live rock? Would the cooked live rock even have anything that would decompose? I am hardly getting any algae in the tank, but maybe I haven't waited long enough for the nitrites to build up.

Now, usually this would be easy to figure out with Ammonia and Nitrite test kits, but I have another problem. I'm extremely cheap. In an established tank, you don't need to keep checking for ammonia and nitrite because they won't show up unless you all of a sudden have a bunch of dead, decomposing fish and corals. I don't want to go spend $16.99 for a cheap ammonia test kit that has 75 test when I would use less than 5 tests. Then I would have to buy a nitrite test kit too, just to make sure. I would be nice if there was an ammonia / nitrite / nitrate package testkit with 10 tests of each, so that people could cycle their aquariums without having to spend $50.

Looks great, but needs some colour and movement...

Regardless, I decided yesterday that my aquarium needs some life. I figured I could at least get some Turbo, Astrea, or Margarita snails, and maybe I would be lucky and the LFS would have a nice small dottyback or firefish or a pair of clownfish for a good price. Unfortunately, our saltwater fish store here in Nanaimo closed down because they were moving to a different city. Thankfully there are two more pet stores that carry saltwater fish. I went to one in the mall, who had just moved last week, but they were still in the process of setting up their tanks. The marine section looked small, but much cleaner than previously. I'm excited to see if they will carry some nice livestock. So, off to the other store. This one, however, recently changed ownership, and they inherited a few large, algae covered marine tanks filled with plastic plants, poor lighting, and many large, sickly looking Regal Tangs for way too much money. They aparently had snails and crabs too, but I could not find a single snail in any of the four tanks. But for $4.99, I decided to wait until the other store has some, or until I can make a trip to Victoria. (Dirty aquariums in pet stores are a pet peeve of mine, but I'll save the rant for another post.)

In the end, I came home empty handed. I found a cheap ammonia test kit made by SeaChem that you are supposed to leave in the tank, giving you a constant ammonia reading anytime, but I want to do more research on them before I buy it. I guess I will just have to be patient and spend the money to get some test kits to make sure its safe to add livestock. Next week I'll add fish!