yep.. all except cichlids are going to ougrow the tank... even a hystrix or retic could outgrow a 180.. and imo cichlids are not good tankmates for rays. you could do some mid sized dither types with small rays long term, but expect the rays to pick them off periodically so i would be wary of adding expensive dithers. I just upgraded my retics to a 120 and know a 180 wont house my female for life if she keeps growing at the rate she is. ( good thing we're buying a house hopefully before winter so i can build a pond in the basement before spring )
ide stick to some nice larger cichlids unless you can upgrade to 300-500 range in a year or so.
and be honest with yourself. yeah the fish aren't overly expensive but you will put alot of money into feeding them reguardless of what you do. i hate getting fish then haveing to part with them after putting a bunch of money into them, you never make back what you put into a healthy fish. The only exception is very rare and desirable fish, most fish just aren't.
if you really like arrows a Jardini may be fine in a 180 for life as a sole inhabitant. but its pushing it from what I understand.
I suggest reading the stickies of each subforum for more exact info on the fish you want.. most will advise against putting these fish together, or even in a 180 for life.
