What brand? Dimensions? Date of purchase? Etc..,
Edit: i think i know what you mean, the brace in the middle is wiggly? Right?
The brace in he middle is to support lid you gonna put on the tank, as a matter of fact its wiggly posture is not going to affect the stability of the lid. Nothing to worry about. My 125 Juwel Rio got the same brace. And i believe that tank brace id the thing that is going round the tank top and bottom, the middle bit i call plastic strip.
omg im some sort of genius! I figured it out all by myself! I should be issued some sort of award here!?? Just a joke if someone likes bit of humour