Seawater – The Most Important Thing

Just about everyone will stop and look with admiration at a marine aquarium. Marine aquarists will of course, but those who do not possess one will also gaze. It’s a very magnetic picture, Mother Nature’s lifeforms within such a confined space. It’s an achievement for the aquarist without doubt, but is it as difficult as it could appear?

There are three types of marine aquarium: first the fish only, second the mixed coral reef, third the reef with corals only. Statistics are not known but the guess is that the mixed coral reef is the most popular followed by the fish only. No doubt there will be a few coral reef with no fish type of aquarium. They all have one thing in common, salt water. Wow, that’s a revelation! However, that is the number one key to success with all types of marine aquarium – high quality seawater. Whatever the system, seawater should be at as high a quality as possible.

The fish only system allows for more fish than either of the other two types. This is because fish, generally speaking, can remain healthy in seawater that is not at as high a standard as required in reef systems. There is a limit of course and that limit must be adhered to or the quality of the seawater will deteriorate excessively. The way that aquarists measure the seawater quality is by monitoring pH, salinity, ammonia, nitrite, nitrate and temperature. This is straightforward enough as easily used test kits are available for ammonia, nitrite, nitrate and pH, test equipment is used for salinity and temperature. All the requirements are easily covered. Provided the tests and equipment show the seawater to be within the permissible limits all should be well. Seawater movement is also required and some include this in seawater quality. The fish need security to avoid stress so often a rock aquascape is included. All the fish need security, that is a cave or crevice to call their own, so the amount of these counts towards the overall fish number. Stress can lead to illness. One important point is growth – in the excitement of purchasing that beautiful fish growth is sometimes overlooked and this leads to later problems such as overcrowding and pollution. Seawater quality needs to be maintained by monitoring and regular partial seawater changes. The fish also need light to see and be seen and this can be easily provided by two marine type fluorescent tubes preferably on timers.

What of the least popular aquarium, the coral only reef. It’s the least popular because most home aquarists can’t resist having fish. This is understandable as they display varied beauty and provide movement. However not having fish provides advantages: fish pollute naturally from the food processes (including overfeeding) and this produces pollution. So the aquarist with the corals only reef system has the immediate advantage of seawater quality being easier to maintain. The same checks are required to confirm this quality as in the previous paragraph, plus additional checks as required, for example calcium. Corals have a need for higher quality seawater so the requirement for checks remains plus the need for regular partial seawater changes. There isn’t any problem with fish potentially predating on corals so any suitable coral (suitable means final size and compatibility with others) can be included subject to easiness to keep, some corals are difficult to maybe impossible. Seawater movement is also important and is higher than in the fish only system. There is one area that is very important indeed and is a close second to seawater quality and this is lighting. A couple of fluorescent tubes won’t do! The corals need specific stronger light so a mix of marine fluorescent tubes, as many as the aquarium will house including reflectors is required. The lighting type used also depends upon the depth of the aquarium. So in the reef only system the problems of pollution that fish could create have been lost making the control of seawater quality easier. The disciplines of regular seawater testing and partial changes remain.

The final system type is the coral reef with fish, or the mixed reef system. This is the system that many are tempted to obtain having seen one in a friend’s house or at a dealers. This system is the most difficult to keep, or better potentially the most difficult. Why potentially? It isn’t really difficult to keep a mixed reef provided the requirements are observed, exactly as is required in the fish only and coral only systems. The presence of fish with a coral reef makes for more difficulty because of the mentioned natural pollution plus possible overfeeding. Also the fish must of course be suitable for a reef system, they aren’t required to go and nibble at the corals! The lighting, as in the corals only type, needs to suit the corals. Seawater movement also needs to suit the corals. The fish will be happy with this. Very importantly, the number of fish need to be restricted to around half that of a fish only system and it is also important to know the size the fish will grow to as this impacts on the number to have. Fish security shouldn’t be a problem as there are less of them in a mixed reef system so, plenty of nooks and crannies. It’s very important that seawater quality monitoring is done in this type of system.

So the choice is there. It’s very important to do the research and be patient. Rushing will not be helpful and could, at the worse lead to failure overall. Poor planning could also lead to the stress of fish and loss of corals. None of this is required. The information is all there on this website and many others. The reward for patience, research and planning is the creation of a beautiful marine aquarium, one that a visitor might see and think ‘Wow, how lovely, I wonder if I could have one of those….’



Seawater – The Most Important Thing
5 (99.73%) 74 votes

Leave a Reply