I use 5 gallon paint buckets you can buy at wal-mart or rubbermaid plastic containers for larger reservoirs. I don't know about the buckets, but I've read that rubbermaid containers are made from food safe plastics. In several crops of using the same paint bucket, I don't notice any appreciable wear to the plastic. That plastic is the same kind used to make sea kayaks and they stand up extremely well to salt water.
Oh! and nothing I've grown has tasted like plastic either.

A lot of those durable buckets are made from #5 plastic - my black 5 gallon bucket is that I use for a reservoir. #5 is food safe. Check the little recycle sign on the bottom of the container to be sure it is #2, #4, or #5 plastic - they are the safest.

Now THAT is some useful information.
Thanks plantboy!

No problem. Plastic is controversial in some areas, and although the following link may strike a cord with some, it does have a useful list of plastic types and known problems with them:

http://www.lifewithoutplastic.com/factsonplastic.htm

It is this list and similar ones that persuade me to stick with #2, #4, #5. All of that said, I think my ebb and flow tray is probably #6 - something that I'd like to change someday once I find a way to do so. Many drink bottles from the grocery store are #1 - so you can only do so much.

Ideally I'd like to experiment with hydroponics that doesn't rely so heavily on plastic parts, but that is a huge challenge and more work since plastic is so convenient.

Instead of PVC pipe I am considering the possibility of using HDPE - the #4 plastic pipe. I am also fairly certain that the black poly tubing used in hydroponics is pretty good too, I think.

Yah - I use a few Rubbermaid plastic containers for reservoir tanks and feel comfortable with them.

What I am most interested in is producing custom size trays to optimize the available area in my 7X8 foot grow room. For instance I am interested in making trays that are
3' long x 8" wide x 8" deep
to try growing carrots and beets. Now those are dimensions you just won't see being sold at hydro shops.

That being said - I am torn between fiberglassing homemade plywood boxes (which are quite easy to make and work with) or trying to coat said boxes with other materials.

So - anyone out there making their own fiberglass trays and are you certain that they are safe to use with slightly acidic nutrient solutions?

What about that plastic/rubber something or other that is used to line the bottoms of ponds/fountains? Maybe that could be used, along with some silicone sealant (food grade), inside your wood boxes.

I think the plastic liner inside a wooden box sounds like the best way to make custom sizes.
I know you can buy large boxes of powdered HDPE (I uses to work in a rotomold factory)but I'm not sure how you'd heat it or apply it once it was melted
though if you could, I'm sure it'd be a great container.
how about bamboo? has anybody considered using that in lieu of pvc piping. find someone who has some and I can just about guarantee you'll find someone who'll give you as much as you want.

Bamboo sounds cool though it will deteriorate with constant contact with high nutrient water.

I'm using EPDM liner in plywood growbeds for my Aquaponics. Don't try and cut then seal the liner into the corners, just fold it neatly and it works well. Especially for media filled flood and drain systems. Bulkhead fittings big enough to go through and seal around the plywood work in such a situation as do uniseals.

Look for fish places. Many products that are fish safe are also food safe. You might be able to find some fry rearing troughs that would be good for Hydroponics. Aquatic EcoSystems in Florida has lots of stuff that is great for both Fish and Hydroponics. They are where I got the uniseals and good priced bulkhead fittings that work through the liner/plywood.

Here is a link that might be useful: My Hydro page