Cheers.
If you sand bed is too deep you can get a build up of anaerobic bacteria which will eventually release a gas that is harmful to your fish. It can come out when you disturb the sand after you have left it for a while or it can even bubble out on its own. It happens where there is no oxygen in compacted, deep sand beds.
Someone who knows better will be able to tell you more (or correct me, haha). Either way, deep sand can be tricky, and it is better going for a lesser depth.
But there lies the problem, in that the one bad thing with these UGJs in a Malawi tank - ENDLESS DIGGING exposing the jets.
ps. Malaysian Trumpet Snails do a fine job of sifting through deeper sand. They are cheap, breed like rabbits, only come out at night and won't be touched by the fish.
