Polyester Resin vs Epoxy Resin in Aquarium Use

[dogstar74]

I've heard it suggested that you should only use Epoxy Resin in Aquarium situations. Is the Polyester Resin toxic?

I understand that the Epoxy resin forms more crosslinks thus is a harder finish and that's what to use if you are building a plywood tank. I also understand that Polyester resin forms strands that make it more flexible than epoxy resin. But once cured are they both inert, or will the Poly resin poison the water? Will the poly break down?

Thanks to all who can respond.
Aaron

[dogstar74]

Just a friendly nudge

[SmithZero]

The polyester resin will not poison your tank, but it is also not waterproof by itself. I used fiberglass with polyester resin to do my first plywood build, and covered it with a layer of epoxy from us composites.

I just started building an enormous plywood tank and will be using polyester resin again, but I am using liquid rubber to seal it this time. The tank is just too large for the epoxy to be affordable.

[BeanAnimal]

The epoxy resin is a superior product for our application due to its strength and adhesion properties. While both chemical resin families have an endless number of forumulations, in general most epoxy resins will be suitable, but many poly resins will be unsuitable and absorb water. In general both families will create an inert end result.

So as a rule of thumb, it is easier to use an epoxy product and derive the expected results as choosing and properly applying the polyester product is more prone to problems.

[dogstar74]

Thanks, Both of you. I was hoping to hear from you Bean, as you are the one that suggested Epoxy not Poly. That is what prompted my internet search as well as this thread. Thanks for the input.