he only wants to keep one fish...a twenty nine gallon is more then enough space for one convict...those dwarf cichlids need special care...in my opinion if you want to keep a single fish in your tank I'm pretty sure you want something that is going to be entertaining and beautiful...and gets the size that your looking for...convicts need almost little care to none...all you need is a filter...water...water conditioner and a heater...that's all...you don't have to worry about ph and all that other stuff...just do your regular water changes every week...you don't even have to wait for your tank to finish cycling...there that hardy...trust me...I own convicts and have since I was young...this is the fish for you