The So-Called Old Tank Syndrome

New tank syndrome is well documented, in fact there is an article on it on this website ( It is where the aquarist has been impatient and has added livestock either in too much quantity in the first place, or has added livestock in ones or twos but has left insufficient time between additions. In other words, the bio-filtration has been unable to cope as it has not had the time to adjust to the bigger load. This problem doesn’t happen so much nowadays possibly because of better education, the widespread use of live rock, and highly efficient protein skimmers.

Old tank syndrome is a totally different kettle of fish (so to speak!). The aquarium could have been running for years, so the bio-filtration will be well matured and fully geared up to the load it needs to handle. The equipment has been in use for a long time and has never given trouble. The aquarist has noticed that it just doesn’t look as good as it used to.

Often the aquarist cannot fathom out why this should be, and this is understandable. Routine seawater changes and general maintenance are done. The livestock is fed as usual and looks healthy enough.

The problem could well be with the aquarist him/herself. When the aquarium first started all was excitement, it was new, there was something happening all the time. It could have been the bio-filtration maturing, the addition of the first fish and then ongoing fish, the corals going in and settling and all the rest. Watching a captive reef settle and develop is terrific.

There lies one possible reason. There comes a point when the system is fully stocked and the aquarist, who has done the proper research, knows that to increase stock would be incorrect. The corals have grown over a period and been successful, so there isn’t a need for anything else to be added. It has been like this for a long time.

So the aquarist does maintenance week in, week out. Doesn’t complain of course, as maintenance is a responsibility, don’t do the maintenance – give up the hobby. There is pleasure generally in seeing the reef, but something is missing, and that’s the excitement and sparkle of it.

Taking things further, the success of the system can actually be a factor in old tank syndrome. Corals have grown, and done so sufficiently to alter the seawater flow patterns in the display aquarium. Consequently, some corals do not have sufficient flow and are showing the result of it. If the system uses piped seawater flow, such as from canister filters, a return pump in the sump and the like, the pipe internal diameter may have been reduced by deposits. This in turn reduces the amount of seawater that is being moved. There are consequences.

Though general maintenance is done, is the aquarist as punctual with new lights as before? Or what about activated carbon changes? Or what about cleaning the decorative sand bed? Or what about feeding the deep sand bed (DSB) (if it needs it)? Or what about regular cleaning of the protein skimmer? The list can be extended.

So old tank syndrome is not a danger of some disease or other malady possibly appearing after x number of years. It is a reduction in attention from the aquarist because the aquarium has become ‘just there’ rather than exciting.

There’s no need. A little bit of attention, such as some checks into possibly required cleaning and some careful cutting (“fragging”) of corals and the like should return the aquarium to its previous glory. When the aquarium perks up, so should the aquarist.