Old Tank Syndrome – The Big Mystery

Through cause and effect, many conditions with an aquarium can be somewhat predicted.

If someone sets a light to be on for ten hours a day, it is a safe bet that a heavy amount of algae will develop.

If one does a decent sized water change every week and doses on a regular basis, then it is also likely that they have a healthy aquarium.

But “Old Tank Syndrome” is a difficult prediction. It doesn’t show symptoms which point to the condition.

The main thing that gets noticed is that nitrate levels don’t go down, even after large water changes and reduced feedings. Increased algae is seen which isn’t remedied long term by the addition of snails and other clean up crew. Then overall water quality begins to decline in other parameters which do not sustain corals, and the fish start getting slower and sick.

Over time, the pieces to the puzzle fall into place and one can look at “Old Tank Syndrome.”

Old Tank Syndrome: Why That Name?

The name, even the existence of the condition, is a point of contention among hobbyists.

It usually refers to the decline in water quality over years caused by a buildup of decaying wastes not being removed from the aquarium and continually polluting the water.

Some say that it is just a matter of time. Some hobbyists say that if the aquarium were deeply cleaned frequently enough, it wouldn’t happen (and therefore shouldn’t be called “Old Tank Syndrome”).

Whatever the name, the condition of “Old Tank Syndrome” needs to be treated.

Identifying Old Tank Syndrome

Diagnosing this condition in an aquarium, in my experience, comes after other steps have been taken to treat an identified issue. It is usually high nitrates which will not come down, even after multiple very large water changes.

Reducing nitrates involves removing detritus (fish poop and other organic waste that hasn’t dissolved). The aquariums our technicians have seen with this issue have all shared something in common. The rocks inside the tank were arranged in such a way that well over 75% of the sand was covered by rock. On average, only 15% of the sand was exposed to where a siphon could get to it. So nearly 85% of the detritus in the aquarium could not be removed.

That much detritus remaining, accumulating and decaying over time is eventually going to catch up with the aquarium. It could be months. It could be years.

It could also be machinery gradually failing, fish and corals getting bigger and producing more waste, or other factors. A technician is going to look at all of these and try to remedy them before diagnosing “Old Tank Syndrome.”

Treating Old Tank Syndrome

The remedy for “Old Tank Syndrome” is risky by nature. It will can great results, and/or great problems to deal with.

At our company, this process requires authorization by management. We want to make sure that this is absolutely necessary before we move forward with it.

The remedy’s object is removing the detritus that has not been removed over time. Rocks which have been lying undisturbed and collecting detritus underneath them have to come out. Many of these rocks have been in place for years, and moving them can release detritus directly into the water. So all livestock is remove before any of these rocks or old detritus gets disturbed.

A massive water change is performed after the removal with a thorough siphon vacuuming to remove the detritus. This is a long and slow process. The technician has to patiently move the siphon through all of the sand to reduce any disturbance and release of detritus.

There is a high likelihood that ammonia will be released into the water during this process. After the vacuum is done and the water and rocks are back in place, the water is tested for ammonia. If ammonia tests positive, the livestock is moved to a holding facility until the water stabilizes. If it tests negative (zero) the animals are acclimated and returned into the aquarium.

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