What plywood thickness do I need to help support my aquaria?

[saint_abyssal]

I've been planning a rack of aquaria for a while now. I'm going to use a Uline widespan wire rack with wood laid over the shelves to better distribute the weight. My original plan involved large tanks supported by sections of "two by" lumber laid across the rack. Since then, I've revised my plans to use smaller tanks as pictured in the diagram below. I was hoping to be able to use thinner wood, like plywood to give me some more head room in the shelves, but I don't know how thin I can go before it's too weak to support the tanks. What thickness should I go with? Or do I need to stick with the original "two by" plan?

 

[Andy Sager]

I've been planning a rack of aquaria for a while now. I'm going to use a Uline widespan wire rack with wood laid over the shelves to better distribute the weight. My original plan involved large tanks supported by sections of "two by" lumber laid across the rack. Since then, I've revised my plans to use smaller tanks as pictured in the diagram below. I was hoping to be able to use thinner wood, like plywood to give me some more head room in the shelves, but I don't know how thin I can go before it's too weak to support the tanks. What thickness should I go with? Or do I need to stick with the original "two by" plan?

I would go with at least 3/8" ply for the top shelf of 10s and 1/2" ply for the other 2 shelves because they will be heavier. Be sure to cut them so that they fill the shelves entirely but especially at the borders where the tanks will be sitting. Make sure you are using the wire racks under the wood or else you will need to use the 2x 4 method for stability in the midsection. (FYI, the particle board option is a waste for under fish tanks. My boards wilted just from the humidity of being on my outside porch. ) Go with the wire and ply on top of it or skip the wire and use thicker plywood. ) Remember, freshwater weighs just under 8 lbs per gallon then you need to add the weight of anything that is the tank and also the weight of whatever fish you are going to put in them.