Are you aware that the Chinese Algae Eater get large up to 10" although I've never seen one over 5.5"
whats the need in this?
anyway, yea a chinese algae eater is fine with sharks. and yes, both fish can be a little temper mental but its the siamese algae eaters that shouldn't really be kept with sharks as these are alot more stream-lined and shark looking so the other shark will most probably see it as a threat.
Red finned shark, when you say this, are all the fins red? or just the tail. if all fins are red, its a ruby shark or a rainbow shark. the other is a red tailed black shark. both fish can be aggressive but the ruby shark has, in my experience, always been less aggressive as the RTBS. dont know why.
neither shark get too big. both are 5/6 inches and, like the chinese algae eater, will get more terratorial/aggressive (if you will) as they get older.
You can put alot more than people think with these sharks. Nothing with long, droopy fins (such as a betta) should be kept with either fish and also nothing that wobbles when swimming (such as a betta). angels are fine with both sharks as well as rams, barbs, rainbow fish and just things that are fast enough, if it need be, and nothing the shark would be tempted to eat. goes with most fish really though.
almost any mid-water fish would be okay and maybe, if i dare, all surface fish, such are butterfly fish, would be okay because ruby sharks often stay on the bottom of the tank unless its looking for food or "cleaning" the tank.
all in all, you just need a cave or two and something big enough the shark would be proud to call his own. they should keep themselves to themselves this way
how big is the tank btw?
and what fish, if any, is there in the tank?