Disease, the word is enough to make an aquarist shudder. However, though the threat remains, disease is not so likely nowadays because of the increase in containment quality with capture, transport, sale and final home. The threat is still there though.
The first action to combat disease is in fish selection. Observe the fish very carefully, all of the fish including breathing. Fish obviously vary but something untoward usually stands out. Watch breathing rate, check scale covering and fin quality. Do fish other than the ones of interest show signs of trouble? Any clear doubts? Don’t buy until satisfactory answers have been obtained. If there isn’t a satisfactory answer, don’t buy even if the fish of interest appears ok.
To reduce the threat even with apparently healthy fish, don’t put them straight into the display aquarium, use a quarantine aquarium. This is a smaller system with a little very basic rock decoration (so the fish can hide and reduce stress) where any disease problem can be dealt with without danger to the main display system. This applies particularly to the reef aquarium as diseases are very difficult to deal with because of corals etc. This is because some disease cures, copper for example, will kill coral life. Definitely not wanted! Put the purchased fish into quarantine for a minimum of two weeks, much better four. If all is well they can be transferred. If not then a cure can be applied without endangering other life. Quarantine for new purchases is necessary when the final home is a reef system and is highly recommended for a fish only system. The purchase of a quarantine tank isn’t that expensive. Of course there needs to be a heater and a circulation pump, plus adequate biological filtration. Protection of expensive purchases, remembering that natural life is being protected, is really worthwhile. When not in use the quarantine tank can be put away out of sight, but it’s there just in case.
Some believe that the use of ultraviolet (UV) light in the display aquarium is good. It is though not a necessary piece of equipment. A pump moves seawater at an appropriate flow rate past a UV light. Any small life forms that are hit by the UV light are killed or damaged. This reduces the danger of disease, but it doesn’t remove it. Obviously for the organism to be put out of action it must pass the UV light and there are plenty of places, particularly in a reef system, where seawater flow is low and organisms will not be dragged into the input of the UV unit. UV unit use is good but not a sure fire anti-disease method. It will also damage or kill beneficial organisms. (Biological filter organisms will not be harmed as they are static in the biological filter media.)
Let’s have a look at just three disease types. There are others and advice can be found on the internet or in hobby books for them.
Marine Ich. The fish look as though they have tiny white spots all over them, or partly so. The spots start with just a few, perhaps one or two and look a little like grains of salt. The fish could well scratch itself on decorations as the spots are an irritant. Treating this disease is reasonably straight forward using copper, but again not in a reef system and preferably not in a fish only system. There are alternatives remedies available but research is required to ensure they are effective. Dose the seawater according to the manufacturer’s instructions, follow the instructions carefully. With this disease it is best to treat all the fish not just those that show spots. This is because the parasites are for a time free swimming and if apparently healthy fish are left in the display aquarium they could be infected thus negating the curing process. The life cycle of these parasites is that they grow on a fish, fall off, reproduce, then become free swimming looking for a host. After reproduction they’re more numerous. If the parasites can’t find a host in four days or so they die. So it’s clear that a quarantine aquarium for new fish – from the very beginning – is worthwhile protection from serious risk.
Velvet. This is very similar to Marine Ich except the spots are much smaller. Eventually they make the fish look as though they’re covered in fine dust. The treatment is by copper. Again, alternative treatment may be available but checks on effectiveness are required.
An important point is that none of the medicated quarantine seawater, definitely with copper and a reef system, must enter the display aquarium. So when treatment is complete the fish must be removed from the seawater completely and re-introduced to the display aquarium. If temperature and salinity are kept the same in both systems then problems shouldn’t occur.
Fin Rot. This problem can be identified by noting fins which appear whitish in colour and maybe have die back. This could be caused by one of two things. First, seawater quality. As has been said on other occasions, seawater quality is the number one requirement. If the quality has fallen, put it right by seawater changes and keep it correct. The second possible cause is fin nipping by another fish. This can only be proved by patient observation. If fin nipping is noted then the offending fish will have to be removed, protection from this quite drastic action is to ensure all fish are compatible before purchase. If the fin rot continues then fungal rot could have started, this is very contagious and the suffering fish will need to be removed for treatment in the quarantine tank.
The disease problem is always a possibility, it hasn’t gone away. Happily disease doesn’t rear it’s ugly head too often nowadays and there are many aquarists who never have a problem. The maintenance of high quality seawater, appropriate quality feeding and ensuring as far as possible that all fish are healthy and compatible before purchase are essential. Having a quarantine system for incoming fish and the ability to separately treat discovered disease problems is also good.