substrate

I have a lake malawi setup that I use crushed coral. My Ph is constantly between 8-8.2. There are also cichlid substrates, both gravel and sand that you could purchase, that will keep your ph at constant higher ph. You have to make sure that you wash it thoroughly before a add it to the tank.

About your setup, you can put pretty much anything you want in it, as long as you have plenty hiding places. You could use a variety of rocks, but you should soak them for a couple of days, in the tank water, but outside of the tank, to make sure that the ph won't be affected. Slate, limestone, texas holey rock, lava rock, and tufa rock are some examples that you might consider. Also, driftwood could be a nice touch. Once again, you should soak them to get some of the tanins out before you incorperate it into your tank. The tanins won't hurt your fish, but will color your water. If you get your own rocks or driftwood, you might want to boil them first.
I hope that helps a bit. Good luck.

If your leaning toward a rift lake set up, don't worry about boiling the rocks, you want your pH to go up anyway, and the extra minerals leaking into the water most likely won't hurt the fish at all. As for substrate, try to get a sand, crushed coral in my opinion is the worst thing you can use. Here's my reasoning, cichlids from Malawi and tangyanika (sp may be off on that) like to dig, they can't do that safely in crushed coral as they may very well cut or injure themselves. The sand however, which is a natural substrate for the, won't bother them at all, most fish infact seem to perfer the sand over anything else. The sand also has an added benefit of having a much larger surface area for your beneficial bacteria to inhabit. Adjusting the pH for a higher reading is very easy, baking soda can be used, and you don't get the fluctuations like you do with a chemical that lowers the pH. As for how much to use, I would suggest getting about 1 gallon of water, and slowly add a small amount of baking soda, testing the water each time untill you get the desired pH. After that you know how much you need to add per gallon.

Crushed coral is perfectly fine for a Rift Lake tank, as is aragonite sand and just about any gravel substrate. I have 9 or 10 Malawi tanks with crushed coral as the substrate, and there are absolutely no problems with it. It buffers the water nicely, boosting KH and stabilizing pH.

As for boiling rocks, the reason this is usually suggested is to kill any unwanted parasites or microorganisms, not to remove it's buffering abilities.

I personally use baking soda to buffer water in my Rift Lake tanks, but only as one of several buffering additives. By itself, baking soda tends to get used up pretty quickly and isn't sufficiently stable. I like using a carbonate source, like AragaMilk or something similar to buffer the water better.

I don't really think that a sand substrate vs. gravel or crushed coral will make much of a difference in biofiltration. In a properly filtered tank (a must with cichlids) there should be more than enough biofiltration capacity in the filters, making the substrate not so imporant in that regard.

If you don't make it too deep, crushed coral or aragonite sand make great substrates for rift lake cichlid tanks. Crushed coral will take pH up to about 7.8 - 8.0, while aragonite sand will take it a bit higher.

HTH,
Jim

Yes i agree, with sand or crushed coral its really personal preference. I have 4 rift lake set ups... one with a crushed coral pre-made mixture, one with sand/crushed shell from the beach (naturally mixed), one with plain sand, and one with sand and oyster shell (unnaturally mixed). There have never been any indications of injuries in any of the tanks and they all dig equally in the stuff.

i like the plain sand the best simply because its the most natural looking.... but adding crushed shell into it gives it a nice effect

as for buffering i use baking soda in the new water added to the tank.. and the crushed coral/shell takes care of the rest.