Many aquarists no matter what type of system they are running, fish only or reef, use more than the display aquarium. The obvious example is the sump.
Of course the extra aquarium doesn’t have to be just the sump, it can be one intended for other purposes.
An extra tank could be fitted alongside, above or below the display aquarium. For seawater movement gravity will play a part, a pump a part, and an overflow a part. The only requirement is the space to set it up, assuming the space below the aquarium has been used for a sump.
The additional aquarium can be any size and any shape, provided it meets the space requirement and also the decorative one if it is within the living area. If there is a lack of space and it is practical, supply and return pipes can run through a wall. Often doing this permits a larger extra aquarium to be fitted.
Once fitted, as with a sump the first advantage is the increase in seawater, the more of this there is the better. This is because the gallonage to livestock ratio is improved. It has to be remembered though that if the extra area is to have livestock this advantage will be reduced or removed.
If there isn’t a DSB (deep sand bed) already then the new area could have one. Perhaps the area could be used for the macro algae Caulerpa to assist with the removal of nitrates and phosphates. If this is the case then the algae needs to be fairly regularly and carefully harvested.
If the aquarist keeps a captive reef then the fish that can be kept are restricted to those that are reef friendly, for example fish are not required that could see coral polyps as lunch. Provided the additional aquarium is large enough, it could contain say a few butterfly fish that are beautiful but generally unsuitable for a reef display. There are cautions. First, the additional aquarium as said is linked into the system. If too heavy a bio-load is placed in the additional area, then the overall seawater quality could reduce and have a detrimental effect on the reef. The fish numbers might need to be restricted to perhaps half of maximum. The second caution also concerns the additional bio-load; can the bio-filtration deal with it? If there is any doubt then additional capacity would need to be provided, either by aquascaping the new area with sufficient live rock or providing an additional canister filter.
From time to time aquarists come across something that is not required in the display aquarium for whatever reason. A good example is a mantis shrimp, which is not desirable because it is an efficient predator. Yet the mantis shrimp is an interesting creature in its own right. Some aquarists purposely purchase one because of this. Providing a home for one in the additional aquarium is straightforward, the shrimps are not too fussy. A sand bed the shrimp can burrow in and a few rocks are fine. The effect on seawater quality is low so there isn’t a danger of trouble with the reef.
If the display contains fish only then the additional area, if it is large enough, could be used for more fish. Perhaps a predatory fish, such as a lionfish, which cannot be housed with the others would be suitable. The volume could be stocked with a full bio-load as there will not be an effect on the original display. Again, care must be taken with the bio-filtration, ensuring that there is sufficient capacity. Fish present the highest challenge to the bio-filtration system.
Then again, there are creatures that are not suitable for the reef or fish only systems, but could do well in the additional aquarium. Among these are seahorses. The seawater flow rate in a fish only or reef system would be too high, and in addition the fish present would eat the food before the seahorses had a chance to feed. So an aquarium could be set up with rock and perhaps Caulerpa to house these strange and fascinating creatures. The load on the bio-filter will not be increased a lot and seawater quality should not be adversely affected.
There are other livestock possibilities for an additional aquarium, and also advanced possibilities that an experienced aquarist could consider.
Whatever is done with the additional aquarium, if livestock are involved then attention needs to be given to seawater movement that is suitable, plus some lighting. The flow in and out of the aquarium will not usually create sufficient movement, and the easiest fully acceptable route is two powerheads subject to requirements. If corals are not involved then two fluorescent tubes are usually enough to provide sufficient light.
There is one additional use that the system linked aquarium is not suitable for, and that is quarantine. When new fish (and other livestock) are purchased it is a good idea to use a quarantine area to give time for recovery from the ordeals of travel. Stress is high and there is a danger of disease and other problems. The time provided permits the livestock to feed in peace and build up their immune system. If a disease breaks out it is much easier to deal with. After three or four weeks, all things being well, the livestock can go into the display aquarium.
If the quarantine aquarium is linked into the display system then there isn’t any quarantine as the seawater is circulating throughout. Any parasites and other nasties are likely to find their way into the whole system which would be a real problem. Also, how could fish that have developed ‘white spot’ or ‘velvet’ be treated with copper? For a start, the medication would be diluted as the whole system seawater volume is involved not just the quarantine area. If a captive reef is present then invertebrates cannot tolerate copper. And so on.
It could be thought possible to use the additional aquarium for quarantine if the in and outflow were stopped for the quarantine period, thus protecting the other livestock. However, again what if copper has been used for an outbreak of disease? All the seawater in the quarantine area needs to be thrown away of course which is easily done, but what of residual copper? Also, can there be certainty that there aren’t any surviving parasites? The quarantine area would need to be stripped down.
Finally, a quarantine tank needs to be available all the time, in case of unforeseen trouble never mind newly purchased livestock. It cannot therefore be used for any display. So it is best kept entirely separate. The tank does not need to be large.
An additional aquarium linked into the system, with attention given to bio-filtration as mentioned if necessary, can provide the aquarist with many possibilities previously unavailable because of livestock compatibility issues. Additional livestock or additional filtration, the system will be the better for it.