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For those of you who have thought about using plexiglass for the lid of your tank...

I did it because plexi is easy to work with--you can cut it or drill holes or whatever. I was concerned that it wouldn't be as rigid as glass, and it isn't. Soon after installing it started to bow down into the tank, which was rather annoying. Also, silicone won't stick to it long term, so you can't use silicone to make a hinge between the two pieces.

So I assumed that the plexi was just too flexible, and that was why it would bend down into the tank (due to gravity). So then I figured if I put a support in the middle of the span of plexi, it wouldn't bow. What I found was that it still bowed UP off the support on each side (contrary to the direction gravity was pulling it)! It turns out that the bowing of plexi has more to do with it being wet on one side and dry on the other causing one side to expand and the other side to stay put (causing the bowing)...

I've screwed the plexi to some rigid pieces of wood to keep it from being able to bend, but it is probably a temporary solution.
 

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i broke my glass lid a while back, and used plexi for a temporary solution... you are absolutely right about the bowing... mine did the same thing... ended up having to just go and buy a new glass top.
 

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The thicker sheets will not bow on you. Yes the thicker the plexy the harder it is to work, but it's nothing some powertools can't take care of.

They DO sell the hindges for the glass tops by themselves.. i believe they are $5.00. I just ordered two from petsolution.
 

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I been using them(thin flexiglass) on my 75G and have had no problem like bowing. :-? :D
 

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The plexi bows due to the temp. difference between the room and the water. The farther from the water, the less bow you will get but it will still bow to some extent. Also depends on the width of the piece.
I have 1/4 plexi on my tank. 2 pieces about 20" wide and i supported them with 1x1 wood on the ends. I still have about a 1/2" bow across this width. If i added 2 more wood supports along the length it would probably stop most of the bow (like a box), but it's there to keep the heat and fish in the tank and does it's job.

Eventually i'll get around to having glass cut for it, but i just picked up a 125 and have to build a stand, hood, and get it up and running.
Gotta love craigs list
 

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I am having this happen as well with A couple pieces I use to keep the cats out of my 55 right now. I am going to be building a top with alot of bracing and will post up some of my results in a couple weeks. I was at my Plexi Suppliers here in town and They have a custome acrylic aquarium with a couple hoods thicker then 1/4" and have bowing problems. Any way I think acrylic would be fine it just needs bracing. I will keep you posted.

Curt
 
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