An example of how a tank might cycle.

Your tank may cycle faster or slower than this.

• Stock the tank with fish at no more than ½ its’ full stocking capacity. This is calculated by using ½ inch of slender-bodied fish per gallon. Only the body is counted when calculating the length of the fish in inches.... don't count the fins!

• For example, the ½ stocking capacity of a 10-gallon tank for cycling would be 5 inches of slender-bodied fish.

• Fish that are good choices for cycling are danios, guppies, goldfish, convict cichlids, firemouth cichlids, kribs, cory paleatus, cory aneus and white clouds.

• Fish that are poor choices for cycling are most tetras, angelfish, discus, clown loaches, oto cats, gouramis, bettas and any expensive fish.

• If you cannot pick a fish from the good cycling choices above that you will keep or find a home for after cycling is finished, then you should do fishless cycling or use Bio-Spira™.

• If possible, seed the tank with a few handfuls of gravel or some filter media from a previously cycled tank. This will jump-start the cycling process by adding some of the required bacteria to your tank. Your tank will cycle without this seeding, but it may take longer.

• Bottled bacteria products are not likely to be useful, except Bio-Spira™, which can be expensive and difficult to find but well worth it!

• Ammonia levels begin to rise.

• Ammonia levels continue to rise. Ammonia, even at low levels, can be very damaging to fish, especially if you are keeping your fish in water with a higher pH. Ammonia becomes more toxic as the pH is higher. However, do not use products to lower your pH.

• If your fish show signs of ammonia poisoning (gasping at the surface, rapid gill breathing, bleeding around the gills, darting about the tank, sluggish behavior and poor appetite and/or refusal to eat) action must be taken immediately to relieve these symptoms.

• You may see a ‘bacterial bloom’ during this time, in which the water looks cloudy. This is not harmful to your fish and will clear in a few days, but be sure to check the ammonia level.

• Ammonia peaks, then begins to drop.

• Traces of nitrite begin to appear.

• Ammonia levels continue to drop.

• Nitrites continue to rise.

• Nitrites can also be harmful to fish, though not quite as bad as ammonia.

• If your fish shows signs of nitrite poisoning (gasping at the surface, rapid gill breathing, darting about the tank, sluggish behavior and poor appetite and/or refusal to eat), action must be taken immediately to relieve the symptoms.

• Ammonia levels drop to zero.

• Nitrite levels continue to rise, then peak, and then begin falling.

• Nitrates may start to appear.

• Nitrites continue falling.

• Nitrates begin to climb.

• Nitrite levels drop to zero.

• Nitrates continue to rise.

• Your tank is now officially cycled!

• The good bacterial colonies have grown in proportion to support the current bioload (i.e. amount of fish and their waste) in the tank.

• Nitrate levels will continue to rise until you take action to reduce them.

• Fish may survive for a long time with high nitrate levels, but they won’t be as healthy. They may become stunted, more prone to disease and will be less likely to spawn.

• Regular partial water changes are the way to control nitrates. The amount and frequency of water changes that your tank requires (e.g. weekly 10-25% water changes) is dependent upon keeping the tank’s nitrate level below 25 ppm and ideally, keeping the nitrate level at 10 ppm or less.

• Do not vacuum the gravel until the tank has been completely cycled for 2 weeks.

• Add a couple of fish per week until the tank is fully stocked (that is, to total one inch of slender-bodied fish per gallon).

• Check your water parameters (pH, ammonia, nitrite and nitrate) weekly during this time or at any time the fish are showing distress and take corrective action.