Glass Lid and Evaporation

[BaleKlocoon]

I would really like to cut down on the evaporation in my 90 gallon tank with 20 gallon sump. I'm wondering, does the majority of the evaporation come from the 48" by 24" exposed surface on top of my tank? Or does most of it come from my sump? If putting a glass lid on top of my tank will reduce my evaporation by 50% or more, then I think I would like to do that. But if most of the evaporation is coming from my sump then I guess there isn't much I can do about it.

On another note, I haven't started growing any coral yet but would like to eventually. How bad is the glass lid for coral? I've read somewhere that a glass lid can reflect up to 30% of the light, so couldn't I just combat that with a stronger light? Any other downsides to the glass lid? I should get plenty of gas exchange with my sump/protein skimmer.

 

[Daddi0]

On my reefs I feel that the air exchange at the surface is very important to keeping a healthy system. This is why I go topless. Yes, the skimmer does add gas exchange, but I think the more exchange the better. You dont mention if you have an ATO? These are easy to set up, cheap, and make maint. a lot easier. It also helps to keep things more stable.
Cheers! Mark

 

[Jonviviano]

I have had my glass lids on my 72 bow front for about 4 years now. DIY LEDs sit on top. Corals grow great, but some compensation might need to be made in the brightness of your LEDs. The only way to tell this would be with a par meter, although i believe it would be minimal. I believe Evaporation has been reduced by at least 25%, probably more. I also cut a few small peices if acrylic to fit over my sump. Not totally covered though as i still want some gas exchange. The only issue i have with my lids is gross algae, mold growth on the underside. I am persistent in keeping them clean but i think it is inevitable.

 

[mcgyvr]

In general the more surface area the more evaporation..
More turbulence can also create more surface area too..

In general I would guess that more of you evap is happening at the display tank vs the sump..

In general there should be zero problems covering up the display tank with a glass top provided you have an uncovered sump and skimmer..
I would not seal the display tank "tightly" but a top with some openings should be just fine..

In general an acrylic top is better as it transmits more light vs plate glass..
However acrylic if not braced properly will bow due to moisture absorption,etc...

I loose like 2+ gallons a day in my 80G tank.. I plan to create a braced acrylic top in the near future to cover up 95% of the tank and expect zero problems doing so and expect to cut evaporation quite a bit..

In general I like to say in general

 

[MurphyLong]

I have glass tops on my 125 to stop jumpers first, and cut down on cooling and evaporation as a second. (My wife keeps the house in the 60's almost year-round)

I was losing about 5g per day without glass tops, and now I lose about 1g per day with them. I also have a small fan drawing in fresh air to the stand. Whether or not gas exchange is an issue, who knows, but the only loss I've experienced was when I left the lid open for 5 mins and walked away, my diamond goby went carpet surfing behind the tank.

 

[Frogmanx82]

I don't believe gas exchange is an issue. If you have a sump you are getting plenty of air sucked down the drain to the sump. Not only does that mix air with the water, it means you are getting fresh air drawn into the area under the glass.

Second you have a protein skimmer. More than enough air exchange is going on.

Regarding evaporation, I have my tank covered about 60% and my sump covered about 80% and I get a half gallon a day evaporation on a 90 gallon tank. If I go to 95% coverage on the tank I get about half that. For sure the cover on the sump is cutting down a lot of evaporation as I can see plenty of water condensed.

 

[mcgyvr]

I don't believe gas exchange is an issue.

It certainly can be if you fully seal up the system..
But the point is that you can seal up quite a bit of a tank and still have sufficient gas exchange capabilities..

Just like I can trap someone in a fridge with a small airline and they will stay alive for quite a while.. :lol2: ok.. maybe too much..
Dear FBI.. That was just a bad joke..

 

[Frogmanx82]

It certainly can be if you fully seal up the system..
But the point is that you can seal up quite a bit of a tank and still have sufficient gas exchange capabilities..

Do you see how much air is getting sucked down to your sump. In no way is there enough of a seal to keep fresh air from getting pulled in over the surface of the water.

 

[MurphyLong]

It certainly can be if you fully seal up the system..
But the point is that you can seal up quite a bit of a tank and still have sufficient gas exchange capabilities..

Just like I can trap someone in a fridge with a small airline and they will stay alive for quite a while.. :lol2: ok.. maybe too much..
Dear FBI.. That was just a bad joke..

Chest freezer works WAY better.