Hey everyone,
I have been assisting our good friend Pat with his new 125 Gallon setup and he has asked me a few questions on when he can start moving his fish in the tank. He has been getting conflicting information (as most of us do) from local sources and online ones.
I replied to his concerns and thought that many of his questions are reflected in many new posts in the forum. I thought I would place my response here for you all to read. It gives a little more insight into the cycle process without my usual long-winded technical gibberish.
Here goes:
Hey Pat,
I wouldn't add the fish in just yet, no matter what anyone says it isn't the amount of time that's passed, its the toxicity levels in the tank.
When testing your tank you want to pay attention to the Ammonia level and the Nitrite level. These are the two hazardous chemicals that are toxic to fish. When your tests show 0 ammonia and 0 nitrite for a week straight, then it is ok to start adding in your fish.
This is confusing most times to new aquarists because right after they set up the tank they test it and see no ammonia and no nitrites and think its ok to start adding in fish. This is not the case. In a new tank it is going to take about a week or two until the ammonia level starts to register in your tests. There is normally a two to three week "spike" in the ammonia as it builds up to dangerous levels over time. This is "danger point #1" (about three weeks after setup) where many people's fish begin to die.
The bacteria begin to have a population boom spurred by the excess availability of the ammonia, their food source, and as the population grows the ammonia level falls. As these bacteria 'eat' the ammonia they convert it into Nitrite. This is the point where you begin to see nitrite rising in your tests, and they will continue to rise until the ammonia level is no longer detectable. It may continue to rise for a little longer after the ammonia zeros out, but mostly you should begin to see the nitrites fall soon after the ammonia is gone. When the nitrite levels are spiking, that is "danger point #2" where fish will lose their lives.
The fall in nitrite is caused by the same reason as with the ammonia, a bacterial population bloom. These are different bacteria than the first colony, and will require nearly the same amount of time to overcome the nitrites as the first did with the ammonia. Sometimes nitrites fall faster than the ammonia do though, so just remember to keep testing. The bacteria that 'eat' the nitrite produce nitrate as a byproduct. Nitrates are not as harmful to fish so long as they are kept low enough. Mostly nitrates are going to cause algae blooms and your fish will be fine.
By the time the nitrites reach 0 then you will have completed the Nitrogen Cycle and
then it is safe to start adding fish. Do so slowly, one at a time, so that you do not overburdon the newly established bacterial colonies. Doing so will cause your ammonia and nitrite levels to rise again.
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How long should you wait before adding the fish in?
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Until the ammonia and nitrite levels are 0. (wait at
least three weeks to make sure that you are not determining good levels prematurely.
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What should you look for when testing?
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Ammonia, Nitrite, and Nitrate. Ammonia and Nitrite are the most dangerous. Nitrates you want to keep an eye on so that you can step in before they get out of control.
You should also check for pH, Temperature, Salinity/Specific Gravity, and Alkalinity (commonly referred to as KH around here, and in many hobbiest test kits).
Essentially, Yes. Algae shows that your tank is at least capable of supporting single-celled life and is a good indication that you are off to a good start. It is also a means of knowing that your tank is receiving at least some light and nutrients. In most cases in early setups it shows that you have moved out of the Nitrogen Cycle and are into the Algae cycle.
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Do you need to wait for the cycle to complete before cleaning the algae off the decor?
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No. You can clean the tank to your hearts content. Removing the algae is actually a good means of nutrient export.
Basically the algae 'eat' the waste byproducts from the cycle, and anything else it may get from the water column, and by removing the algae you are essentially removing the waste.
HTH,
Aaron
