I find all of my rocks for my African tanks in creek beds during the summer. Any kind of slate or inert rocks will be fine. If you want to test it but the rock in a bucket of water for a few days then test the ph, if its below 8.0 or equall to your tap ph it should be good to go.
Also some pointers that haven't been covered for your future of cichlids.
IMO dont buy any kind of "mixed cichlids". Big brand store often buys from breeders who give fish tons of hormones so they will loose color after you bring them home and die younger than ones without hormones.
In terms of online breeders I've had good experience with Imperial tropicals, snake river cichlids and Quinn's find but it dosnt mean there arnt many other good breeders out there. Check there websites and decide what you like.
You can go all Male or a female mix. Just go 3 females to one male. Sounds like your going 4f to 1m which is on the safer side.
Keep your pH above 7.5 using baking soda. My mix for my water is 1 teaspoon of baking soda, 1teaspoon of weapons salt, 1 teaspoon of pickling salt per 5 gal. Your baking soda amounts will vary depending on your tap water. My tap is 7.0 and soft.
I attached pictures of my tanks, I only have peacocks and haps but I keep some syndontis in every tank for cleanup and they have a good personality. Also bristlenose will help keep your tank algea free so you you should be set for cleanup. My syndos are are super overweight but they keep the tank spotless.
If you want to overstock your tank I made a thread about a nitrate reactor. You should be able to find it in the filters section.
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