I'm going to go against everyone in this respect and say you shouldn't have medications sitting around the place unless you actually need them. The only exception to this is a fish de-wormer. I de-worm any new fish when they are being quarantined and that is it. If the fish get a disease then I zip out and get some medication to treat them. Unless you live out in the boon docks and your nearest fish shop is 50miles away, it isn't really necessary to have medications sitting around waiting to be used. Most fish shops are open 7 days a week.
If you do have medications that are going to be around for a while, try to keep them cool. Put them in a sealed container in the bottom of the fridge or somewhere that is cool. Don't let them freeze because that will damage the chemicals. Try not to let them get too warm because the ingredients will break down faster. Make sure children cannot get to the medications because most of them are quite toxic.
If you want to use medications in the tank then take out any carbon from the filter before you treat the fish.
To work out the volume of water in the tank
measure Length x Width x Height in cm
divide by 1000
equals volume in litres
When measuring the height, measure from the top of the gravel to the top of the water level. If you have big rocks or driftwood in the tank, remove them before measuring the height.
If you want a broad spectrum medication then try "Waterlife Protozin". It treats whitespot and other skin parasites like costia, as well as bacterial & fungal infections. However, good water quality & the correct temperature for the fish being kept, will reduce and prevent most disease outbreaks.
