I bought a set of racks to put tanks on:

Box said it will hold up to 4000lbs. Unfortunately, the shelves are made of particle board which A)if exposed to water will absorb the water and fall apart and B) by itself isn't strong enough to hold the weight of the tanks full of water.
I have thought of several options but would like some more experienced opinions so please offer me some opinions!!!!
My thoughts: '
A) i could paint the shelves with epoxy type paint to seal them and the brace them with 2x4s underneath but that will take up valuable vertical space.
B) i have SOME experience with fiberglass via surfboard repair so in theory, could i lay out some fabric and glass each shelf? I KNOW it would be water tight, but do you think it would be strong enough to hold the weight... and also, would it be cost effective?
C) buy thick plywood and seal it...
got any other ideas or improvements to mine?
and one more pic of the corners so you can see how the shelf sits on the braces:

thanks!!