Hi! jsho,
It seems you want more of African Cichlids.
If you have very hard and alkaline water, I would just stick to fish out of such water parameters. Geo and GBR are more adapted to softer and slightly acidic water and so is the Pleco.
I'm not saying you can not keep them as you planned. It is your tank after all. I used to try different things when I was young only to come to conclusion Why dont I just give them what they need, their natural conditions they evolved and adpted to.
afra, demasoni (
mbuna; rock dwellers), lithobates and Alunocara (peacocks; free-swimmer) from Lake Malawi.
Cyprichromis leptosoma from Lake Tang (more sensitive than above).
Both Lake Malawi and Tang waters are very hard and alkaline.
Have few questions for you.
Is tank well established (cycled)?
What are
pH,
ammonia,
nitrite readings from tests?
What kind of rocks and substrate?
I dont think GBR is sensitive when given what they need and well stablized at lfs after long trip being shipped from Far East (unless bred locally).
I know that some people will/have said that they have kept gbr in such hard and alkaline water and even spawned. Yes. I've seen it.
If one understand Renal Functions (kidney) of organisms, one may think otherwise, just like advantages of salt in F/w.
Although different fish will react differently to salt, adv far outweighs the disadvantages if done properly.
I read lots of disadv of salt in f/w from members. I have not responded to any yet but happens to read this article and wanted to bring it to our members.
If possible p/u a copy of Jan 2009 FAMA. There is an article by Paul Speice about salt in F/W.
I thnk this concept will convince why we should give fish what their physiological/anatomical needs are to see them live long and happy life in our care.
Pardon me for long post and hope this help you out a bit!