Aquarium cycling

The initial period in which a new aquarium develops the bacterial colony necessary to sustain life. It lasts 3-6 weeks and should never be skipped.

Detailed explanation

Maturation is the most critical period in the life of an aquarium. A newly set up aquarium does not have nitrifying bacteria: any fish introduced immediately will produce ammonia which will not be processed.

The classic method involves setting up the complete aquarium (filter, heater, substrate, decorations, water) and adding a source of ammonia without fish. You can use pure aquarium ammonia, rotting fish food, or a dead shrimp.

Ammonia rises to a peak in the first few days. It then begins to drop as Nitrosomonas bacteria colonise the filter. At the same time the nitrites rise. After a few weeks the nitrites also start to drop. When both ammonia and nitrites are stably at zero and nitrates are present the cycle is complete.

Accelerating products (bottled bacteria) can reduce times to 1-2 weeks if used correctly. Seachem Stability and Dr. Tim's One and Only are among the most reliable.

In marine aquariums, maturation with live rock is an excellent method. The rocks already carry an established bacterial population. Die-off (death of some organisms during transport) provides the initial ammonia. You wait until ammonia and nitrites are zero.

Silent maturation (silent cycling) is a technique where the aquarium is planted heavily from day one. Plants absorb ammonia directly, avoiding spikes. It only works with bright light, CO2 and lots of plants.

Don't rush. Rush is the aquarist's number one enemy. Better to wait an extra week than cry for dead fish. Use the maturation time to study the species you want to host.

How it is measured

Ammonia and nitrite tests every 2-3 days. Maturation is complete when both remain at zero for at least 3 consecutive tests with slightly increasing nitrates.

Related terms