Plexiglass aquarium covers?

I tried using sheets of Hardware store plexiglass to cover my fish tanks, but the plexiglass eventually bows and drops down toward the water. I'm wondering whether using thicker plexiglass would overcome this problem. Since I have multiple tanks on a rack, I'm not interested in hinged, glass aquarium covers. I single sheet--made of material that I can't knock over and shatter--would really work best for me.

Has anyone else gone the plexiglass cover route? If so, can you tell me what thickness and type of plexiglass you used and where you ordered it?

I'm thinking of finding a place to order it on line, and then having it pre cut and sent to me.

Thanks!

Rather than use thicker sheets, you can reinforce thin sheets with thin strips of plexi attached along the length of the sheet. If you don't mind welding them on yourself, you could probably get your plastics shop to give you some strips from their scrap pile. A tube of Weld-On #16 will weld a lot of strips, and is only bout $7, so you'll save compared to buying thick sheet.

Newt - have you tried this and does it not bow? Seems to me that acrylic (plexiglass) of ANY thickness bows over warm water. Polycarbonate is less bow-prone, but more $$. I use glass (and try not to drop it)

Rather than use thicker sheets, you can reinforce thin sheets with thin strips of plexi attached along the length of the sheet. If you don't mind welding them on yourself, you could probably get your plastics shop to give you some strips from their scrap pile. A tube of Weld-On #16 will weld a lot of strips, and is only bout $7, so you'll save compared to buying thick sheet.

I have not tried it, I always use glass. I think two thin layers laminated together will be less likely to bow than a single thick layer. This is an assumption based on characteristics of wood, but I think it will hold true for plexi as well.

I have not tried it, I always use glass. I think two thin layers laminated together will be less likely to bow than a single thick layer. This is an assumption based on characteristics of wood, but I think it will hold true for plexi as well.

Not sure if this is essentially the same material or not, but I used the plastic pannel from a recessed flouresent light, the textured 2'X4' pannel that fits into the ceiling, to make a lid for a 20 gallon. I cut it to size and glued 2 pieces together for reinforcement, but it still bows. I wonder if a strip of wood (or a few strips) attached to the top would keep it from bowing.

Use eggcrate and cut to your desired size, can be made to fit nearly any tank. About $10 for a huge sheet of it. I painted some with Krylon Fusion black, worked great on it.

You can also drop food through the holes easily, and rest lights on top of it no problem.

Edited by GreenLakeYak, 03 December 2009 - 11:17 PM.

Thanks. Egg crate doesn't stop evaporation. I'm wondering if cementing/expoxying it on to plexiglass would stop the plexiglass from warping.

Use eggcrate and cut to your desired size, can be made to fit nearly any tank. About $10 for a huge sheet of it. I painted some with Krylon Fusion black, worked great on it.

You can also drop food through the holes easily, and rest lights on top of it no problem.

You could have eggcrate cut to fit the inside bevel of the aquarium, then cut out a plexiglass sheet and lay it on top of the eggcrate. The eggcrate would stop the plexiglass from warping, even if it was just laying on top of it. You could go as far as to seal the plexiglass onto the eggcrate if you really want to prevent evaporation, but I think you could get away with just having it rest on top or maybe just taping the edges to the eggcrate.

Not sure how big your tanks are but buying eggcrate, plexiglass and sealant may end up costing more than just buying a pre-made glass cover would be.

I remember reading that if using plexiglass only in order for it not to warp under those conditions it would need to be over .5" thick, very expensive at that thickness.

I'll try to get some pictures of the way I'm using eggcrate, might give you a better idea of what I'm talking about.

Edited by GreenLakeYak, 04 December 2009 - 02:05 PM.

Are you using plexi-glass or some form of HDPE - high density polyethylene? A sheet of HDPE is very rigid and would not bow substantially, maybe not at all, with a cross brace or two. Usually is even more rigid the less surface area it has. I use it for all sorts of abusive things, like bottoms to view buckets. It's available at Lowe's, is easily cut by a jig saw or smaller circular saw with a fine toothed blade.