Does anybody know how much a glass or acrylic top reduces your lighting (wpg) on a tank? Assuming you keep the top clean...

I've been putting an acrylic lid on my tanks at night, which reduces my daily evaporation by at least half. Then I started thinking: Why not just keep the lid on? I'm also thinking about getting some fish that like to jump, so I'll have to do something to prevent suicides. When I take the tops off in the morning, there is a ton of condensation on the top -- my initial guess is that the condensation sure would cut down on the light getting to the tank, but maybe not.

I think if they are kept clean it should not affect it that much. If the condensation is heavy and permanent, maybe, but I think you are okay.

Many people have tops and have good growth..........

Thanks, Gerry ... I'll give some thin acrylic a try and see how it goes. I'm also hoping that using tops will cut down on the humidity in my room -- with three tanks, the moisture builds up pretty good.

Be careful when using thin acrylic for a tank top. I noticed that 1/8" acylic on a 24" tank sags in the middle. Also I believe acrylic absorbs water and will warp. For that reason I use 1/4" inch acrylic when I use it for a top. Even at a 1/4" I think the superior light transmission characteristics make it a good choice.

I agree about the sagging with thin material.

My trickle filter used CHEAP covers and they bowed within the first 3-4 weeks of use......

Part of my project plan is to replace these with DIY ones that will incorporate better stronger acrylic and a sock filter for each. Really made me mad to think the covers were so cheap compared to the rest of the filter.....

Sorry, off topic and end of rant

IMO i believe its fully sealed, i agree it would sag due to thickness and very slight chance due to heat depending on how close your lights are to it ect..

I read a post some time ago on another forum debating the benefits of acrylic vs glass tops. This person seemed to know what he was talking about.

I owned an acrylic tank and it was made of high quality acrylic. It may be that the quality and chemical composition varies from one product to another. I'm sure there is someone out there who can clear this up.

Absorbing some water doesn't mean water leaks through. I googled this and found that acrylic absorbs .03% of its weight in water. That is very little, but it will cause the material to bow towards the water side. Comparison Table for Plastics.

The table says % and .03, how do you know that it is referring to its weight?

Looking at the table, if it is weight then nylon absorbs 9x its weight it water?

No, nylon absorbs about 7% of water, whether by weight or volume is immaterial in this discussion. If it were 9 times its weight it would say 900% in that table.