I have a 30 gallon aquarium and cannot find a divider specifically marked for this size aquarium. Anybody know what size will fit? Dimensions are 11 3/8'' x 17''
You may need to get one for a 55 gal and trim it to fit... I think a 55 is 12x18. Sounds like you have an older 30 gal long. Don't see many of them anymore.
Look at one for a 55, and see if you can cut it to fit (before you buy it)