Stocking The Saltwater Aquarium – Part 1

In Part 1 a fish only aquarium will be covered. In Part 2 the reef aquarium will be looked at.

It is assumed that the [tag-tec]aquarium[/tag-tec] is fully set up with all necessary equipment running and checked, and the filtration is initially mature.

First of all, the net gallonage of the aquarium should be known. By aquarium I mean the display aquarium. If a sump is part of the system, then the net gallonage of this should be excluded. Why is this? On the face of it, running a sump which adds extra gallons seems an opportunity to stock additional fish. Not so. The sump seawater is a water quality enhancement over and above the basic requirement for biological filtration. If the gallonage of the sump is used in the calculation of fish stocking, then much of this water quality enhancement will be lost. Also, it must be remembered that the fish will live in the display area. Including the sump could lead to some overcrowding.

Not good.

The aquarist needs to consider the type of fish he/she wishes to keep. Will they be small shoaling species such as damsels? Will they be larger species such as angel and surgeon fishes? Perhaps butterfly fishes? Or is there a desire is to keep a predator or two, a lionfish is an obvious example? Stocking considerations depend a lot on the answers to these questions. Get the mix wrong and, as an example, a lionfish will enjoy a damselfish lunch. Also the larger the fish kept the less the number of [tag-tec]marine fish[/tag-tec].

Once the decision on the type(s) of fish to be kept has been made, then those particular fish need to be researched. This research will answer questions such as – are they territorial and to what degree, are they shoaling species, will this fish mix with that fish, do the fish have any special feeding requirements and can the aquarist meet those requirements? The fish may all be compatible as far as aggression/territoriality is concerned, but are any fish noted as timid feeders? This could cause problems if the others are bold feeders. In addition, and important, what size can the fish be expected to achieve given time within the aquarium?

Also, is it fair to keep the type of fish in the aquarium? What does that mean? It would be wrong to keep a surgeon fish in a 24″ long aquarium. They need swimming space – a considerably larger aquarium. In the research the aquarium needs of the fish can be answered. Also consider the need of the fish for security. Where do the fish go at night? In the aquarium there needs to be plenty of hide holes, caves etc, of various sizes, so all the fish kept will feel more secure and not stressed. The colours of the fish and their health can be much enhanced by paying attention to this.

The aquarist has narrowed down the fish list to the ones that are suitable for the intended aquarium, taking into account aquarium size, fish compatibility, any special needs, security etc. Stocking the fish is a fairly straightforward process. Obviously, the aquarist can keep more small fish than large ones (remembering as already stated that the fish are going to grow). The general guideline for stocking fish only has become more complicated over the last few years, because of the better filtration methods used, the advanced and better support equipment available (example: skimmers), and the higher water quality achievable. This generally means that more fish could be kept. However, it is best to keep fish numbers low on initial stocking so that the bioload is not excessive on the filters. Then fish can be added slowly (provided all is well). Why slowly? Mainly so that the biological filtration can adjust to the increasing bioload successfully.

So, to stocking then. Stocking is based on inches of fish per net gallonage of the display aquarium. When we talk of inches of fish, this excludes the tail. The initial stocking rate that I personally recommend is 1″ of fish to every 6 gallons of seawater. In a mature fish only system this is under stocking. Remember, though, that we aquarists consider the welfare of our livestock our prime target. This stocking level should not cause any problem.

However, there is also a caution as well!

The fish may well be compatible in all ways, but note during research any fish that is deemed more timid than normal. That kind of fish can go in first with others. The fish will then be ‘at home’ and more confident and later additions will be the newcomers. There is no requirement to put all the initial fish in at once. They can go in as they are obtained up to the suggested initial stocking level.

Three months after the final fish of the initial fish stock went in, if all is well, if water quality has been maintained, then the rest of the list can be gradually purchased and introduced (allow the biological filtration to develop). Always keep an eye on water quality and stop adding fish if there appears to be any kind of problem. The full fish load, I would suggest, is 1″ of fish for every 3 gallons of seawater in the display aquarium. So, the fish load has been gradually doubled. Again, remember to monitor water quality and fish health.

In fairness, there is controversy over stocking rates, with differing views. However, I believe that stocking as suggested will allow the fish to be healthy and settled. As the aquarist watches the aquarium, as experience grows, he/she may have the confidence to add more fish.

Don’t overdo it!

Now here’s a quiet word in the ear. If the [tag-tec]marine aquarium[/tag-tec] hobby bites and causes addiction, it is likely that the sight of a marine reef aquarium will set wheels in motion. If so, the only way to achieve a reef aquarium if the fish only aquarium has ‘reef unsafe’ fish, is to start another aquarium, or sell on your beloved fish collection.

You have been warned!