Plexiglass Over Tank

[FishinAround]

Is it OK to cover the the top of my tank with plexiglass, I think it's 1/8". I have a 120g reef tank with a 2x150 HQI MH and (2) 2x65 PC's. I would like to put the plexiglass between the top of the water and the bottom of the lights. I would also like to put plexiglass over the sump with the macro-algae. I'm evaporating water at the rate of 1-2 gallons/day. Are there any issue with light diffusion? Will the plexiglass get too hot? Any other ideas to reduce evaporation? Thanks for the help.

[sir_dudeguy]

no do not put anything over the tank. 2 gallons per day in a 120 is perfectly fine. All you have to do is pour it in the sump.

If you put a piece of plastic directly underneith those mh's its gonna get either really hot, or just melt (prolly the first..for a while..)

It will also block too much light.
Also tho, those arent even the main problem with doing that. When you completley cover up the stuff, you're not gonna get any gas exchange, which will more than likely drop your pH. Plus, when water isnt evaporating (and yours isnt even going that much. I get 1-2 gallons a day in my 55) the tank is gonna raise a few degrees temperature wise.

Evaporation is NOT a bad thing. Its not really doing anything good for the tank other than keeping it cooler, but it isnt bad like most people put it out to be. If topping off the water is the problem, get a topoff unit. Or better yet...make one! :) you could easily make one. just look in the diy forum if you want one. But all i do is top off once in the morning and once in the evening.

[mg426]

I have my 125 covers made out of lexan 1/4 inch. I have had them on my tank for 3+yr, However my 30 gal refugium is open and so is my 30 gallon sump. I have my fans blowing on my sump for cooling in the summer I was losing around 3 to 4 gallons /day. I also have MH lighting but its 8+inches above the covers, and have cooling exhaust fans in the enclosures. The set up works for me. I have great PH 8.3 lights on 8.15 lights off.

[barjam]

1/8 is way too thin. I have 1/4 inch over my 75 with only 160 watts of NO lighting and it warps.

If you have a skimmer I wouldn't worry about gas exchange.

The only reason I am running with a plexi top is because I started my tank up with tap water and I really don't want to evaporate anything for now. My RODI will be here friday and the cover comes off.

[sir_dudeguy]

ya what mg said will work, because the sump and everything is still completely uncovered. I still woudnt put anything in front of the lighting tho. Its just gonna warp/melt and block out light.

but barjam...what does using tap have to do with covering the tank and not wanting evap? Whats that gonna do?

[drummereef]

I did this for the longest time for the reasons you are stating, but found that having an auto top-off device is all that is needed to solve the problem here. There are issues of light diffusion and gas exchange if you cover the tank. If you have jumpers just put some eggcrate on the top and you'll be good to go.

[mg426]

I am looking at egg crate for next summer, I just never got around to doing it. I agree that open top is most likely the way top go. I just had good luck with a remote fuge and sump with open top. I will probably being saying the same thing next year LOL

[sir_dudeguy]

egg crate...i wont even start lol. anyone who's read a thread about that knows that i dont like it :)

But imo auto topoffs arent even as nessesary as people make them to be. Especially when you have a 120 thats only gettng 1-2 gallons evap per day. Thats really not that much and wont cause much of a swing in...anything really. Like i said, just top off at least once a day, 2 is better if you've got the time. If you dont have any time to top off your tank even...then i dont see how you could have time to even care for the rest of the tank. Just whenever you're home top it off. If you're not home enough to do that tho, then i guess a topoff would be good.

[mg426]

Whats the deal with egg crate?? I been hearing about it forever just never got around to trying it out.

[drummereef]

Theres mega-controversy over egg crate on here, but it's served my purposes and many others well. It's basically the grate that goes over fluorescent lights. People use it for many purposes in this hobby from tank covers to platforms in frag tanks.

[mg426]

Yeah i know what it is I have actually had my hands on it at the hardware store just never got around to installing it. whats the mega controversy all about ??

[sir_dudeguy]

aah dang...i knew someone would ask! lol.
kinda (ok way) off topic, but basically, it sucked for me. I tried 3 different types of it, tried all 3 on both sides, and it blocked a ton of light still. So basically, when people say that it "focuses" light, i disagree. I did do a little test tho. It DID focus it when the light was w/in 1 inch of it...however, you shouldnt have the lights 1 inch from the water to begin with, and if you raise it up off the water...well..you're basically defeating the purpose of even getting it! :) And also when its really close to the light it got really hot and warped a little bit, so i'd imagine that if it was constantly doing that, it'd proly mealt or something.

The reason for getting the egg-crate in the first place was to keep fish in. I refused to use any glass top or plastic lid because it blocks off 1) evap, and 2) gas exchange.

imo evap is good.. It drops my tank temp 5 degrees, and seeing as im in arizona..thats critical lol. About 3 times this summer people on the local board posted about their tank crashing due to 90+ degree temps.

gas exchange really helped my tank. My pH was low, so i took all my lids off and my pH raised up to a borderline acceptable number (from a very poor number) and then i switched to IO salt and its all good...but the fact is that it raised my pH about 0.3
Simply having those 1 or 2 inch gaps in the back of the lids didnt do jack diddly squat for me.

So i wanted my fish to stay in (this is where i tried egg-crate) but didnt want to use egg-crate or a lid...so i built a hood. Crappy, yes, but very affective in that it allows for perfect ventilation, holds my retro, and keeps fish in. I'm just not very good at building with wood (i've only got a screw driver and a circular saw :) ) but i made one nonetheless, and once i paint it, it will proll look pretty nice, and it only cost 25 bucks total. If theres any interest i can post a pic of my hood. Just a regular rectangular hood but it worked.

[sir_dudeguy]

I do like it for in-tank use tho...like how drummer said...make platforms and whatnot with it. I built a "cage" for my chaeto since i didnt have any other place to put it in my sump lol

[drummereef]

There have been multiple tests done about the light transmision with and without the crate. It seriously gets people enraged when you start debating. Steven Pro did a test and basically said there was little to no difference on his system. But, the debate is out. I use it and don't have a problem.

[mg426]

We are kind of off topic but it is interesting. I have had no problems with my current set up as far as PH and temp cause I keep the fuge and sump open and run the fans over the sump.the window AC helps too. I have had no problems with the lexan covers melting at all, Even under the halides. the exhaust fans really move a lot of air and you can feel the heat being sucked out. The PC actinics get the lexan kind of warm.they are right on the tops. I got the super clear stuff from where I work that passes light straight through with no tint at all. I geuss the egg crate is not the ninth wonder of the world after all.

[mg426]

I was just looking to try something new cause my covers are showing their age.

[barjam]

drummereef do you have the thread where he did the testing handy? I had no luck finding it and I don't want to derail the thread by asking about it here.

[Steven Pro]

<a href=showthread.php?s=&postid=8142070#post8142070 target=_blank>Originally posted</a> by drummereef
There have been multiple tests done about the light transmision with and without the crate. It seriously gets people enraged when you start debating. Steven Pro did a test and basically said there was little to no difference on his system. But, the debate is out. I use it and don't have a problem. Huh? Dana Riddle did the test that showed that eggcrate used nearby the lights will increase the total amount of light going into the tank and my own experience coincides with Dana's testing.