I have a 200 watt submersible pump with a "do not submerge below this line" warning. was thinking a small raft could keep it above water in my food/drain. My air conditioner has a styrofoam tray I was considering cutting a block off. the tray has "PS 06" recycling symbol on it. Do you think it would be safe to put in the tank? I have bluegill & catfish
A submersible pump should be able to be located completely underwater. Not sure what you mean by "do not submerge below this line".
The "PS-06" marking is just the SPI resin identification code (for polystyrene). It should be just as safe or un-safe as any other piece expanded polystyrene.