Old Tank Syndrome
A condition sometimes referred to as “old tank syndrome” can occur in tanks that have been running for a few months, or
The problem tends to occur in aquarium tanks that have one or more of the following:
- Too few or too small partial water changes.
- Excessive dirt build-up, especially in the gravel.
- Too many fish (overstocked).
- Too much food being added (overfeeding).
The problem can occur quite quickly in tanks that are overstocked and/or overfed in combination with too few water changes.
It can also happen in well-established tanks that have been trouble-free for several years, because a gradual build-up of
wastes suddenly reaches a critical level.
The main effects on water quality include very high nitrate levels and low pH levels, but can also include low oxygen
levels and measurable levels of ammonia and/or nitrite.
These will cause fish to look less vibrant than they should, make them less likely to breed, more prone to disease,
and shorten their lifespan (most fish should live several years).
The above symptoms may not be immediately obvious. Often the problem is only noticed when newly added fish die regularly.
The long-term residents have had time to get used to the steadily increasing waste levels, but the high levels will be
a shock to newly added fish.
These problems can be easily avoided, mainly by carrying out regular partial water changes. Regular water changes
help to prevent a build-up of nitrate and replenish the natural pH buffering to keep the pH stable.
Maintaining an appropriate stocking level for your tank size, and careful feeding of the fish can also help
prevent the above problems occurring.