I take it your considering moving over to sand ? All my tanks have sand in them, personaly i prefere sand as a substrate as i think it looks more natural, if you are going this way, then have a look at pool filter sand or play pit sand (kids sand) as they are both suitable sands for aquarium use (wont leech any nasties in the tank) as well as being cheeper than aquarium sand. Your catfish will also prefere a sand substrate over gravel. Do not use builders sand as this can/will contain chemicals that you do not want in your tank. You will not need to worry about the two types of sand that i have mentioned nor aquarium sand as all three are perfectly safe for aquatic life. All you need to do with the sand is rinse it before you add it to the aquarium, and make sure that it is NOT deeper than 1" also you will need to rake through the sand every so often so as to avoid it compacting and traping any nasties, i tend to rake my sand every time i do a water change (every 2 weeks) and find i have no problems. If you need to know anything else about sand just ask
