Any experienced aquarist can understand why a newcomer to the hobby really wants to see some livestock in their aquarium, because those aquarists have been through the same process.
Doing things properly is a patience tester. This isn’t a bad thing because patience is at or very near top of the list of attributes that are very advantageous to a marine aquarist. It starts from the word go. First there is the question of the aquarium size and position and also perhaps a bit of diplomacy with the other half. Then there is the question of equipment and its cost, perhaps when the equipment list was complete and also running costs checked, mainly electricity, the aquarium needed to be downsized a little (in itself highly commendable if cost is a question, better to find out early). Collecting the equipment could have taken a considerable period, relieved from time to time by the excitement of opening another box.
Then the aquarium and equipment are all together. Great, off then! Oh no, there it goes again, slow down, use patience. This is at the stage of livestock of course. The aquarist is well aware of what system it will be, usually fish only or mixed reef (there are some coral only systems about). Having done the research the reason for slowness in stocking becomes clear: the bio-filter. This is the life support for all the life within the aquarium. Without this support it wouldn’t be long before trouble struck, probably with tragic consequences.
The aquarist could be using live rock which is supplied ready for use, or cured (it can be supplied uncured leaving preparation to the aquarist, but the normal is cured). This live rock contains the bacteria necessary for dealing with toxins, namely ammonia and nitrite. These two toxins are deadly and the only acceptable level is ‘undetectable’ or zero. (Live rock should also be able to deal with nitrate within reason, but nitrate is not a toxin in the sense that ammonia and nitrite is.)
Or perhaps the aquarist has chosen a canister filter(s) to provide the bio service. This is fine, though it needs to be remembered that nitrate will be produced by this system and not removed. There aren’t any bacteria present in the canister filter at the beginning, they need to be kick-started. This can be achieved in several ways, though the best is using commercial maturation fluid and following directions.
So the stage is set. Whether it is a ‘matured’ canister filter or live rock, the aquarium should not be fully stocked.
In the case of the canister filter the maturation is primary. There is a bacterial presence to deal with ammonia and nitrite but the bacteria are new and probably few in number. It takes time for them to build and adjust to the full aquarium load. Placing a full aquarium load (or bio-load) would overpower the abilities of the bacteria to cope and disaster would follow. The bacteria would increase because of the high presence of toxins but not fast enough.
What of live rock? This is purchased hopefully with bacteria present. It is fairly certain that bacteria will be present but are there enough to deal with the full bio-load? It must be said that there could be, if the live rock has just been cured and is new for sale. Even then it isn’t certain though. Also, what if the live rock had been in the ‘for sale’ tank for a considerable period, as much of it is? All life needs food and this includes bacteria. If the rock has simply been sitting in a tank then the bacterial count could drop and be quite low.
So we’re back to the beginning, with the words patience and slow. With both live rock and canister filtration, stocking particularly with fish should be slow. This enables the bacteria that are present to have a chance of dealing with toxins which of course is good for the fish and the aquarist. Failure at such an early stage is not pleasant. As time progresses and the bio-load increases the bacteria populations also increase to keep pace and have a good chance of achieving this if stocking is slow. Eventually full stocking is reached and the bacteria then settle down to handling a more or less level load. Once this stage is reached and about three months have elapsed then the bio-filtration can be considered to be stable.
During the stocking period regular testing is required to ensure the bio-filtration is coping. This is easily achieved as ammonia and nitrite tests will hopefully show zero for both. If any reading does appear further stocking should cease and close control on feeding is needed. The readings should disappear and after a week or so of zero readings cautious further stocking can proceed.
During the stocking period routine seawater changes should be completed, these changes continue for the life of the aquarium. The guideline amount to change is 10% of the net seawater gallonage per week. This amount could be flexed once the aquarist has some experience and knows the traits of the aquarium, such as nitrate increase if any.
So what does the word ‘slow’ generally mean in relation to stocking? There are varying opinions though quite often the advice is to ‘stock slowly’ and nothing else, which isn’t particularly helpful.
Corals present a quite low bio-load in the aquarium and it is considered general good practice initially to sparsely populate the reef with the desired corals, which means they are spaced well apart. Later when it is apparent there is space available more could be added. It also gives time for the aquarist to see the extent of expansion that many corals exhibit. Those that do expand, and also those that don’t, grow. Corals of differing types should not touch. A reef that looks overcrowded probably is.
Fish present the biggest load for the bio-filtration to process. When a fish is introduced, feeding also needs to start, so the work of the bio-filtration really begins. The aquarist should have done research on the fish and know their habits and potential final size. It is good practice to put more timid or peaceable fish in earlier than robust and/or more aggressive types.
It cannot really be stated that an additional fish could be placed in the aquarium after every X period. The size of the fish needs to be considered. If a small fish is placed in the aquarium, then of course the bio-load will increase. After a period (see below), if all is well with seawater tests, then a further fish could be added. This also has the advantage that if the initial fish is timid then it has time to settle and become confident in its new home. The next fish could well be a small one too, so the same applies. A further fish could well be larger so it is good practice to increase the time allowed before any further addition, as the larger the fish the bigger the load it places on the bio-filtration. If the fish is an inch larger, allow an extra week. Proceed in this way keeping a close eye on seawater conditions and feeding carefully (meaning minimize excess) and all should be well.
There is a guideline for time periods between fish additions. This is general and not intended to be rigid in any way, particularly if an aquarist is not sure if all is well. In that case, wait! The general guideline is ‘a week an inch’. So if that is followed a two inch fish would require two weeks before another fish is introduced. If the next fish has a length of three inches then a three week period is required, and so on. The fish length excludes the tail. I’m not aware of any scientific evidence supporting this guideline, but it is sensible and works.
If the marine system has been well thought out, once the seawater has been placed into it and livestock is introduced it is the birth of a new mini aquatic world. Everything should be in balance as far as possible. The lighting should suit the corals, the corals should be properly spaced with sufficient seawater movement and the fish should be mutually compatible and suited to the system design, be that fish only or reef. Supporting the aquarium life is the bio-filtration which is absolutely essential.
The foundation for future success is current practice. Give Mother Nature’s bacteria time and they’ll do the job.