Acrylic Tank Cover Warping

[snailpoo]

Hrm.

After my beloved clownfish of three years decided to go carpet surfing, I, in complete, mindless haste, went and got an 1/8 inch acrylic cover custom cut for the tank. The cover was fine for two days, but is now warping downwards.

I'm guessing that this is due to heat from the lights, but am surprised that the heat emitted from a pair of PC lights six inches away could warp the tank cover (especially since the light fixture has its own acrylic cover that is less than one inch from the bulbs).

Is there something else that is causing the warping? Is this fixable?

Thanks!

 

[KathyC]

Have a pic? How big is the tank?
Did you cover the entire top of the tank with it? 1/8 is too thin..the lights probably didn't cause the warping, just the weight of the acrylic could have done it.

 

[snailpoo]

The tank is only 30 gallons, and the acrylic sheet measures 29 cm by 89 cm. While it is pretty light, is the weight of condensation pulling it down, too?

I'll try to get a picture.

 

[KathyC]

At that size it would have warped if you laid it between 2 chairs..
I'd be more concerned with losing oxygen exchange by covering the tank.

 

[Aqua Pro Builder]

It also may have to do with the material of the acrylics. Some brand is easier to wrap.

 

[snailpoo]

At that size it would have warped if you laid it between 2 chairs..
I'd be more concerned with losing oxygen exchange by covering the tank.

There's a 6cm x 6cm hole allowing the filter return, a 18cm x 9cm hole accomodating the in filter box, and 15 or so 1/2 inch holes scattered elsewhere. Is that enough? There's also an overabundance of algae, and the sump isn't covered at all.

After three days, everything in the tank is still acting normal, and the fish are not breathing heavily.

It also may have to do with the material of the acrylics. Some brand is easier to wrap under little heat.

Doh! It's whatever brand the plastic shop on Canal sells.

 

[Eznet2u]

I had the same problem over my 65g freshwater tank. The problem is NOT heat. It's moisture. You used extruded acrylic. Extruded will absorb moisture.
There is more moisture on the water side of the acrylic so that side swells. If you take it out, it will dry out and go back flat. What I used to do, was flip mine every 2-3 days.
I eventually just got a glass cover.

 

[snailpoo]

Thanks for the advice guys!

 

[Acrylics]

I'm a little late to this but Eznet2u was pretty much right on. Acrylic (all, not just extruded) absorbs moisture and will *always* cup when used as a tank cover. The top side will become concave and the under (water) side will become convex as it grows due to moisture absorption. Just flip it over occasionally or use a polycarbonate such as Lexan which won't do this nearly as badly. Best is to just get a chunk of glass if possible.

Hope the fish is better

James

 

[wxl14]

Glass is the way to go. You can get it custom cut also. just remember to clean it when you do your water changes.

try this place
http://elmersaquarium.com/h108glasscover_aga.htm

 

[Aqua Pro Builder]

Acrylic (all, not just extruded) absorbs moisture and will *always* cup when used as a tank cover.

Agreed.

Welcome to MR.
Do you have the same SN in RS?

If so, can you mix something works like weldon #4 that delays the reaction but stronger(like the mix you did) than weldon. I found weldon not strong enough to some brands of acrylics.

 

[Acrylics]

Agreed.

Welcome to MR.
Do you have the same SN in RS?

If so, can you mix something works like weldon #4 that delays the reaction but stronger(like the mix you did) than weldon. I found weldon not strong enough to some brands of acrylics.

Thanks for the welcome
Depends on the brand of acrylic. The only brands I'd recommend at all are Polycast, Cyro Acrylite GP, and Plexiglass G. Most of the others have too many variations in their quality controls to work with reliably. One of these variations is that their mol chain lengths are too so long that the material doesn't break down with solvents well enough to make a strong bond. IMO there is no *good* answer for these materials for most of our purposes; many fabricators will use WO40 but this will not "bite" into off-brands with reliability and can suddenly just come apart at the seams. Due to the variations in some of these materials, simply can't recommend them for pressure vessels of any sort.
I'm assuming you are referring to a brand other than the 3 noted above. If you are working with one of the brands above, lemme know. Hope this makes sense
BTW, yep, same SN whenever possible

HTH,
James