cork + dolomite + eco complete cichlid =happy cichilds?

Do you just like the look of cork? There are all kinds of ways to make caves for cichlids, one popular one is making a grotto (Google diy grotto)
http://www.aquariumlife.net/projects/diy-decoration/7.asp

I'm not sure what you mean by limestone substrate exactly - do you have a brand in mind? That would probably be a white substrate, no? If you're attracted to the look of the Eco Complete cichlid (the chunky, dark substrate) then get it, but I think you pay excessively for the whole "living water" thing it's packed in.

Crushed coral sand or gravel (depending on your preference) would work fine, you could mix it in with a regular substrate like inert sand or gravel. You could get some oyster shell (my Petsmart still sells this as a substrate for marine tanks, their marine section is THAT outdated) and mix it in if you want a chunkier look. Do keep in mind that a pH raising substrate helps some but does not completely eliminate the problem of keeping the water buffered. I think it worked better in the days of undergravel filters, but now without water passing through the substrate, I think it will lose its buffering ability as the tank matures and it gets coated with biofilm. Kind of like an M&M

Aesthetically, cork just doesn't look right in an African cichlid setup, if you ask me. After all, mbuna means "rock fish" so obviously...rocks should be the main feature Also, doesn't cork leach tannins? Easy enough to remove with carbon, but still. Cork would be fine for New World cichlids, but not sure about Africans. I would advise against using it, but perhaps others have done so successfully.

Fortunately, your pH is high to begin with (perhaps why you got into keeping African cichlids?) so you probably won't have to worry a whole lot about it...but do keep an eye out and buffer the water change water if you have to. There is a DIY recipe for Malawi salt mix that is 1/3 Epsom salt, 1/3 baking soda, and 1/3 marine salt mix which works wonders and is economical as can be.

If that's your goal then stick to rocks. I would get some round river rock and sand to replicate the malawi coast.

Eco-complete is OK but i like Caribsea a whole lot better, I would advise against cork as well and go for THR.. But hey have fun its your hobby.. Also the marine sands will do a lot better than crushed oyster shell..

I used aragonite substrate, Looks nice and keeps my ph. At 8
http://m.youtube.com/index?client=m...uri=/&gl=US#/watch?xl=xl_blazer&v=k2AC1Qq2OcI

Sweet