21Ö.Fish-In Cycling Guide
So you went to the store and listened to the employees and let your tank run for a few days and then added fish. Maybe some fish started dying or maybe you started doing research and read up on cycling. So what do you do now? Donít panic. This guide will help you.
First, make sure your tank isnít too overstocked. If you have a goldfish in a bowl thatís going to be a problem as you will never be able to keep up with the ammonia the fish will put out; either return the fish or upgrade to a proper tank size. If youíre not sure whether your stock is adequate, ask on the forum. Ideally you want to start with a small number of appropriate fish which will slowly add ammonia to the tank to feed the bacteria but not enough so that the ammonia becomes overwhelming too fast so that you are doing constant water changes (not to mention the potential damage to the fish).
Next, be sure you have a proper liquid test kit, like the API Master Kit. Test strips are very inaccurate and for a fish-in cycle, accuracy is key.
A good water conditioner/dechlorinator is needed, preferably one that says it detoxifies ammonia, nitrite, nitrate and heavy metals. This will keep your fish safe between water changes (but it is not to be used in place of water changes). Seachem Prime is the most recommended brand and is sold at most fish stores and online.
If you can find some seeded media (filter material from a healthy established tank) it will go a long way into speeding up your cycle by introducing the needed bacteria. Ask friends who have aquariums for some media from their filters, or ask at various fish stores. AngelsPlus also sells active sponge filters from their Angel Fish tanks (be sure it says ďactiveĒ next to it or else youíre just buying a plain filter).
Test the tank daily for ammonia, nitrite, nitrate and PH. At the beginning (the first 2-4 weeks) you may only get an ammonia reading and thatís OK, itís good to always test everything anyway. You may also want to test your tap water for ammonia, nitrite, nitrate and PH as well. If your tap water has some ammonia or nitrate in it for example, youíll have a good idea of what youíre putting into your tank and where your starting from. When you start to see the ammonia rise over .25, do a water change. You want to keep the ammonia level under .25 at all times. Remember basic math: if your ammonia level reads 1 and you only do a 25% water change, the ammonia will only be reduced to .75. It is OK to do one larger water change or even multiple water changes in one day for the protection of the fish. Just remember to add dechlorinator each time and to try to match the temperature of the new water roughly with the tank water (feeling both with your hand is usually accurate enough). Changing water will NOT slow down your cycle (despite the rumors to the opposite); clean water will help your fish live through the cycle.
A note on the API Ammonia kit: it can be hard to read the ammonia test colors on the API Kit. Often, the 0 reading may look slightly greenish depending upon the lighting conditions in the room. When in doubt, move to a better light source. You can also test some distilled or spring water and compare the tube to your tankís test; if they match, the tankís ammonia is 0.
After a few weeks or so youíll notice that the ammonia isnít rising as quickly and may even read 0 each time you test. This is good! But the next phase, the nitrite phase, will follow. Nitrites are as toxic to fish as ammonia and will rise very quickly. Keep testing the water at least once daily and when nitrites rise over .25, do water change(s) to get them lower. This phase is the longest and can last at least 3 weeks so just be patient, youíre halfway there! As nitrite rises you should also check for nitrate. For the API kit, the nitrate test is finicky and can cause inaccurate readings if not done correctly. Shake and BANG both nitrate bottles on a hard surface for 30 seconds and then once both drops are in the tube, shake the tube vigorously for a full 60 seconds and then wait 5 minutes for the result. Nitrate isnít as toxic to fish as ammonia or nitrate but itís recommended to still keep them low; if they start to rise higher than 20, do a water change to get them down lower.
After another few weeks or so youíll test one day and nitrite will be 0. Congratulations, your tank is now cycled! Be careful when adding new fish though; the bacteria in your tank is only enough to support your current fish load. When you add more fish the bacteria need to multiply so add new fish slowly and test parameters daily and do extra water changes as needed.