There are one or two things that are an aquarists nightmare. A good example is an outbreak of so-called marine velvet, often called [tag-tec]Oodinium[/tag-ice] because it is caused by the dinoflagellate Oodinium ocellatum. This is where a few tiny white spots appear on fish and without treatment they increase until the fish are covered. The fish will die without adequate attention. The best treatment is copper, acceptable
Similarly the discovery of a leak can cause severe problems. The severity of the problem can vary however. There are ways to deal with a leak, but they are ‘fingers crossed’ methods. The only real way to deal with a leak is to empty the aquarium and re-seal properly. Sometimes that drastic solution can be avoided. Breaking down a developed reef is not pleasant, never mind the problem of where to temporarily store all the water, rocks, sand and livestock.
When a drip or run is discovered, by noticing a wet carpet for example, the obvious first action is to trace the source. Internal dividing panels can be ignored, as they are not containing the water but just dividing the space within the aquarium or sump. The leak will be one of the joints on the aquarium itself, either a breakdown of the silicone joint or a crack in the glass. Once the crack or leaking joint has been located what action to take can be considered. What will be required is either silicone sealer (aquarium safe type) or epoxy two part resin (again aquarium safe). Also a small bottle of methylated spirits. If silicone has never been used then practice with a little. It is easy to apply if careful.
Where is the leak? Hopefully it will be high up in the aquarium or sump. If it is high enough up then fate has smiled a little. Drain the water down to an inch or more below the leak, as far as possible, and of course the leak will stop. The water should cover the corals, if these are the soft type they will possibly assist by bending a little. Dry the area thoroughly on both sides and leave to make sure it is dry. Get a clean dry cloth and wet an area of it with methylated spirit, but not dripping wet. Carefully wipe the area, inside and out, around the crack or joint. Keep the cloth out of the seawater. The methylated spirit will evaporate very quickly (it is used as a cleaning agent). Now very carefully apply silicone sealant over the crack or failed joint area inside and out, overlapping well, on both sides. Silicone usually needs 24 hours to dry (check the instructions) and forms a strong water proof joint. Hopefully this will seal the area successfully. Of course, if it is a crack in the viewing glass that is being dealt with then the repair will not be invisible. If a crack is being dealt with, then obtaining a small square of glass and siliconing that in place over the crack on the inside with good overlaps will create a stronger seal. The silicone must be continuous to ensure a seal and it is easier if it is applied to the small piece of glass.
What if the leak is low down? This reduces the options somewhat. The aquarist has to decide if he/she is willing to strip down the reef to gain access to the leak. It may be that all the reef may not need to be removed, only enough to reduce the water level sufficiently. If this can be done, proceed as in the previous paragraph. 24 hours will be required for the silicone to dry and heating provision must be provided for the items that have been removed from the reef. If there is sufficient water left in the aquarium, livestock can be left, but again ensure that heating is provided as any return pump in the sump will have to be turned off. Incidentally, if the leak is in the sump and the sump water level needs to be lowered, the return pump can be left running, just remove seawater until the sump level is as desired. (Ensure returning seawater does not splash the repair area.) This is because the sump pump keeps the display aquarium seawater at the correct level, any reduction in seawater will affect the sump seawater level.
If the previous paragraph actions are not suitable, then the aquarist has two options:
A. Strip down the display aquarium completely and repair the leak with silicone as described, using a small piece of glass if the leak is a crack. This is the preferred choice for repair, though obviously there are problems with reef/livestock storage.
B. Consider using two part epoxy putty. This putty is strong and solid and will be much more visible than silicone. The seal is not quite as easy to achieve.
If choice B. is chosen then, first, make sure the crack or seal is as clean as possible. Remove all algae and other debris. Read the instructions on the putty very carefully and mix as advised. If sealing a joint, then apply the putty in a fairly large amount, and spread it out with the fingers so that it is overlapping the joint leak by at least ½”. Ensure the putty is adhering firmly, and has not been pressed thin, it needs to be quite thick. The warmth of the aquarium water will assist the putty to harden, and the water pressure will assist it to adhere. When the leak area is dry on the outside, after using methylated spirits apply silicone. If sealing a crack proceed in the same way. With a crack it again is best to use a small piece of glass. Apply the putty to it first after ensuring the glass is clean by using methylated spirit and make sure the putty goes round the glass without a break and in sufficient quantity.. This repair will be very obvious unless in an out of the way location.
Hopefully, having taken action one way or another as outlined above, the leak will stop and be cured. The aquarist now has time to consider how much faith he/she has left in the aquarium, and if the repair is just too obvious to put up with. Perhaps a new aquarium should be obtained? Of course, this will mean disruption for the reef. If the aquarist feels positive about the existing aquarium, all well and good. If not, well, better safe than sorry.
The problems above refer to silicone/glass aquariums. Having said that, nowadays glass aquariums cause little trouble. The glass thickness to be used is clearly understood, and properly applied silicone is immensely strong. So no need to worry, just enjoy.