I'm trying to build a sump for a 75 gallon tank out of a 50 gallon Rubbermaid tub. This will be a freshwater tank, and I would like to have some floating and/or emergent vegetation in the sump for nitrate/phosphate removal.
Keeping floating plants out of the pump requires some sort of baffle extending down into the water so water can flow underneath to the pump suction without creating a current at the surface to draw plants in. These will be small plants like Azolla, duckweed or similar. Ideally I would also like to have a baffle on the bottom at the beginning of the sump, so that I can pipe water to the bottom and have it flow up over some biomedia like a pile of lava rock, flowing over the baffle into the planted section.
Initially I used sheets of plexiglass with silicone sealant for the baffles. I'm not sure what I was thinking.
The problem is that water weighs a lot, and once filled the tub deformed significantly and broke my seals to the point where the baffles just fell over.
I've now built a 2x4 frame around the top to minimize deformation and hopefully keep the whole thing reasonably in the same shape once I fill it, but it won't be exactly the same shape and I expect that if I attempt the same plexiglass solution it will still break the seals.
What I need is either an aquarium-safe adhesive that could be applied underwater, so I can build baffles after filling and not worry about deformation, or I need to think of some other rigid material I could use that might be self-supporting without the need for attachment to the tub itself.
Right now my best idea is to use brick for the first one, which doesn't have to be watertight as its purpose is really just to guide flow and retain the biomedia in position. For the second, it really does need to make a near seal with the side of the tub since it needs to retain very small plants to prevent pump clogging. I think I could maybe just use wood that I could screw onto the top frame and hang down into the water. That would be easy to cut into shape and easy to install, but I'll need to find untreated wood and it still won't make a perfect seal.
Any ideas?
Keeping floating plants out of the pump requires some sort of baffle extending down into the water so water can flow underneath to the pump suction without creating a current at the surface to draw plants in. These will be small plants like Azolla, duckweed or similar. Ideally I would also like to have a baffle on the bottom at the beginning of the sump, so that I can pipe water to the bottom and have it flow up over some biomedia like a pile of lava rock, flowing over the baffle into the planted section.
Initially I used sheets of plexiglass with silicone sealant for the baffles. I'm not sure what I was thinking.
The problem is that water weighs a lot, and once filled the tub deformed significantly and broke my seals to the point where the baffles just fell over.
I've now built a 2x4 frame around the top to minimize deformation and hopefully keep the whole thing reasonably in the same shape once I fill it, but it won't be exactly the same shape and I expect that if I attempt the same plexiglass solution it will still break the seals.
What I need is either an aquarium-safe adhesive that could be applied underwater, so I can build baffles after filling and not worry about deformation, or I need to think of some other rigid material I could use that might be self-supporting without the need for attachment to the tub itself.
Right now my best idea is to use brick for the first one, which doesn't have to be watertight as its purpose is really just to guide flow and retain the biomedia in position. For the second, it really does need to make a near seal with the side of the tub since it needs to retain very small plants to prevent pump clogging. I think I could maybe just use wood that I could screw onto the top frame and hang down into the water. That would be easy to cut into shape and easy to install, but I'll need to find untreated wood and it still won't make a perfect seal.
Any ideas?
