measure the height under your tank buy 2x4s and cut/or have them cut professionally.
buy some flat L shape brackets (ones you would use to make a shelf or something forgot the name) & some wood screws that are stainless steel
go home put the 2x4s under the tank where the bow is happening use the flat L shape brackets to screw the 2x4s so it wont move when getting something from inside the stand.
(on bottom only, you dont wanna screw where it's bowing cause that might make it break)
also when screwing the 2x4s under the tank try to screw them in where there is already a 2x4 or joist in the stand so its sturdy.
also you can paint it over so it doesnt look to sloppy but this is your choice.
