Marine aquarists make use of varying types of equipment on their fish only or reef aquariums. This equipment is generally reliable nowadays but nevertheless any device has the potential to fail.
There are many canister filters in use for either mechanical or bio-filtration. Though live rock is the bio-filtration of choice for the modern aquarium, canisters are still in use by many for this essential task. There isn’t any reason why they shouldn’t be, though there are drawbacks.
Live rock is able, within reason, to deal with nitrate. In other words live rock should perform the full nitrogen cycle. This is the major drawback with canister filters, nitrate is the end product. This is because the bio-media within the canister is oxygen rich and there isn’t any need for oxygen to be obtained elsewhere. Nitrate reducing bacteria require an environment very low in oxygen which forces them to seek an oxygen supply elsewhere; nitrate is present so oxygen is taken from that which breaks the nitrate down. It follows that an aquarist using a canister filter needs to keep a closer eye on nitrate levels and carry out the requisite correctly sized seawater changes.
Another advantage of live rock is that there isn’t anything to break down, as opposed to a canister filter where there is an electric pump. As already said modern canisters are reliable though recommended models should be sought when purchasing, but what if a breakdown does occur?
Failure of the electric motor means that the whole function of the canister ceases as seawater flow stops completely. When an aquarist does routine maintenance the output from various devices is checked, an operation that takes hardly any time. However, it is more likely than not that a failure will occur at an inconvenient moment. Canister electrics are usually very quiet nowadays and there isn’t any indication of trouble apart from seawater output ceasing. So the first thing is to note the output anytime possible, such as at feeding time and when starting to simply observe and admire the aquarium. It only takes seconds.
A stopped canister filter should be switched off and then on again a couple of times, this sometimes frees up the motor. Don’t count on it though! If the motor does re-start then as soon as possible check the shaft and impellor for debris. However, before attempting to re-start by switching off and on note the comments in the following paragraphs.
Once the output from the canister is noted to have stopped there isn’t any way of knowing when it stopped. This is a worry because involved is the life support for the system, the bacteria. How are they faring?
It could be that the fish have been acting strangely and that is how the lack of seawater output was noticed. If this is the case then the failure occurred quite some time ago as there has been time for toxics to build up in the seawater. The first action is a seawater change, the size of which depends on the severity of the situation. If the fish are really obviously in trouble then 25% is not excessive, more if necessary, and the change should be done as soon as possible. The aquarist should be prepared to carry out a further change if necessary.
The aquarist should ensure that other equipment, namely the protein skimmer and seawater circulators, are working at maximum efficiency to ensure maximum oxygen intake and minimum bio loading (the skimmer should remove substances reducing the load on the bio-filter).
A regime of seawater testing should be introduced. Once the situation is under control the tests can be done once daily, but it is often better and more reassuring for the aquarist to do tests morning and evening. The tests are of course ammonia and nitrite. The only ongoing acceptable test result is ‘nil’ or perhaps more accurately ‘undetectable’.
If it is found that the canister filter electric motor has failed but the fish are not showing symptoms of distress then the failure is probably quite recent. Again, test the seawater and do a change if necessary.
In both cases, fish distressed or not, cease feeding until an effective bio-filter is back in operation.
The speed that toxics develop in the seawater depends to a large extent on the fish numbers present. Corals present a far lower bio-load.
As soon as possible deal with the canister filter. At this point it is known that switching it on and off didn’t work! Ensure it is switched off and disconnect from the tubing. Check the impellor and shaft, there could have been a failure, if jammed the problem can usually be sorted out. If there is a breakage spares are usually available, obtain them by the fastest possible means even if it incurs extra cost. (Obtain the spares from the local fish shop if possible to avoid any delay.) Check that the input and output tubing is not blocked, this could occur over time.
If the electric motor itself has failed then a new canister filter should be obtained (or better two, see below). When the replacement device is available bio-media can be transferred and if required extra added. Until the new device arrives the bio-media already held should be kept within the aquarium seawater preferably in a high flow area so that at least some of the bacteria are retained. When the new canister is running there is a clear need for monitoring the seawater condition, as it will be similar to though not as extensive as maturing again. Seawater quality can be maintained by additional seawater changes, new seawater should be available at all times until the aquarist is sure all is well.
If the canister has been off for a long time do not re-start it and allow it to continue running. Disconnect and drain the internal seawater out completely. Refill and then start and run. This is because there is a danger that the seawater within the canister could be heavily contaminated. If the canister is likely to have been off for only a short period, just re-start. It is worthwhile carrying out daily seawater tests for a week in either case to ensure the bio-filter is effective. After re-start, feeding should be with considerable caution as the bio-filtration may well be weakened and need to re-build. Again, ensure that the protein skimmer and seawater circulation pumps are at maximum efficiency.
To largely avoid a problem such as described, unlikely as it usually is, when the system is designed it is a good idea to employ two canister filters. This will of course mean a little more cost, but the filters can be smaller. Instead of obtaining one which can handle the net gallonage of the system, obtain two. These together in total should handle the net gallonage, but it is a good idea to have both of them a little oversized. They can be routinely serviced alternatively so there isn’t any extra work generated. If the need for canister bio-filtration is removed in the future they are useful for mechanical or other types of filtration.
It is generally unlikely that a modern canister filter will fail, particularly if it is adequately routinely serviced. If it does fail the shaft/impellor could be affected by accumulated debris and/or calcareous buildup, or tube blockages could be present. Observation is the main preventative.