The grow bed has to be strong to withstand the weight/pressure of the grow media and water. I would say 3/4” or 5/8” plywood should suffice. If you live in a colder climate, I would recommend you line the inner part of the grow bed with foam insulation before you install the duraskrim.
On the question of the silicone, I see pet stores selling 100% clear silicone for use on aquariums. You can get a bigger tube of 100% silicone from a hardware store at a cheaper cost.
I am a newbie also with a six month old system.
Thank you for your comments. I will use 3/4 plywood. I was more questioning whether I should use pressure treated or regular plywood. I did some more research on sealants. There is a company that makes livestock safe sealants. I didn't want just a regular household sealants that can leach into the water.
Are you building an outdoor or indoor system?
If the grow beds will be outdoors then pressure treated plywood should offer more protection against termites and the elements. For indoor systems with no danger of termites etc., non-pressure treated plywood or wood could be used.
Good point. The system is going to be outdoor. The growbeds will be 3.5 ft x 7 ft. I am going to build 4 to start; eventually there will be 12 growbeds. I have enough clay balls for 2 or 3 beds. the empty beds will just b deep water culture for lettuce and other greens. Next weekend I will start building the first 4 beds
Any update on the system?
Well, It has taken a little longer to get the system going. I live in Northern California... My area experience about a week of freezing temperatures most winters. I may add some insulation on the outside of the plywood in the future. I dug some footings for my blocks. I needed a way to ensure that they are level. It wasn't too hard and now I have footings for two growbeds. I also leveled out a spot for my IBC fish tanks. I have room for two and may add two more in the future. I have to do the math to make sure that I have enough grow space to filter the water.
Your system looks like it's doing great. t'll keep you posted on my progress.