OK, first I would get rid of the airstone. Not only is it not necessary, but the salt creep it will generate will drive you crazy. What kind of water are you using? RO
? Tap? I would also highly suspect the rock you have in there. Usually, any rock of volcanic origin is something to be avoided. I would get rid of it and replace it with some aragonite rock. If you don't want to spend the $$ for LR
, buy some base rock. I don't know what the slime is, but, again, I suspect the rock may have something to do with it. If it is volcanic, it may be leaching harmful compounds into the water. One other thing I would do is get some Salifert test kits. I would not trust the readings from the Tetra kits. If you can't find Salifert, get Seachem. Lastly, I would buy a copy of "The Conscientious Marine Aquarist" by Robert Fenner. I don't want to discourage you and we will help you get this tank on the right track, but I think you'll need to make a few changes to the setup to have a successful tank.