PlanetCatfish.com

I had a catfish tank about 10 years ago with about every synodontis you could imagine, a whole 54 of them, don't worry it was a 3m tank.

I now want to go back to my catfishes from marines, I've got 2 questions here.

1. What kind of substrate is best for catfishes, pebbles or sand.

2.Can I leave the crushed coral in one of my filters for bacterie growth or should I take it out.

Back then I used normal sand for my tanks, but these days there are all diff kinds of substrates and stones.

to 2. Coral`s are "made" of Na2CO3 and K2CO3 both are alkaline so it bring`s your pH down (~pH8-9 valuation), most catfish`s like pH6,5-7,2. But if you are thinking of putting synodontis from the Tanganjika- or Malawi- lake in that isn`t a problem pH there is ~8,5.

I keep/kept all my Synos in Peagravel, sand, and crushed coral substrates. None were noticably bad. Although my tap PH is 8 and tanks also, so no effect with crushed coral. Sand is prolly the best(not for the filters). But peagravel has never been a prob either. What types you lookin for?

If pH is 7 it becomes 8.
If pH is 8 it will not change, Na2CO3 and K2CO3 then fall out. They just puffer it to 8 or higher

Arent Corals made primarily of aragonite? Thats CaCO3. I'm not sure where you are getting K2CO3 or Na2CO3, as I've never seen those listed in any geology class I've taken, nor are they listed in my geochem book on anything to do with reefs or limestone.