no they wont get baked in fact they will love the extra light, trick is too go slow so move them low and rise them when they are adapted.
i was running a 250w on my 25g cube so i think youll be fine, i also ran a 250w on my 33g zoa tank and a 250w on my 20g long like yours......all these tanks loved the light .
as for fish perhaps a blenny or a goby woud do depends on what you like really, keeping in mind you only have 20g
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