Nice build!! I bet she is heavy though.
1/2" XPVC is readily available for ~$100 for a 4'x8' sheet. Two sheets will get you an 11 tub high 41qt rack using Sterilite tubs with enough left over to build a 24 tub hatchling rack.
Add $50 of heat tape, $25 for some 1" x 4" pine and you are set.
Two racks for under $300- just add your thermostats