View Full Version : no top

10/06/2017, 08:06 AM
I have a 120 gal. tank with a canopy but no type of cover over the water. I seem to get alot of water evaporation. My question is. do I add a glass top over water or are there other options to help minimize water evap?

Thanks in advance

10/06/2017, 08:11 AM
A/c and ambient temperature have an effect on evap... the closer the temp to that of the tank the less the evaporation will be. A/c dries the air out, so increasing evaporation. However, all of that pales into insignificance compared to putting glass on the top... I have a large open top tank and lose 30 litres a week!! So I know how this feels!

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10/06/2017, 08:16 AM
Yes adding a top can certainly reduce evaporation..
However.. realize that gas exchange (oxygen/nitrogen,etc...) is pretty critical in aquariums so there is a point where you can be causing more problems than you are solving..
But if you have a sump with a skimmer down there then thats likely enough exchange and you can slap a lid on the tank..

I'm not sure if there is any real data/experiments on how tight a lid can be before it causes problems..
I always run with no top and just accept evaporation for what it is..
Evaporation also helps with removing heat from a tank (if thats an issue) and reducing evap will increase temps

10/06/2017, 08:39 AM
both replies make lots of sense. I have 2 tanks that are pretty much identical setups. One at home and one in my office. The office tank has a glass top and room temp stays appox. 75-78* steady. the evap seems to be much less than other tank which has canopy and no glass. So that was my reason for asking. I will be ordering a top for the home tank and report back my findings. thanks for the input. :wavehand:

10/06/2017, 01:37 PM
I had a glass top; on my 60g cube (no sump) for about 20 years. I thought it was a good looking tank, but never "great" Then I broke the top. Rather than replace it with more glass, I made a DIY screen top. And never looked back. Literally within days things were perking up. I had never realized what an effect that little change could make. I wish I had done it about 2 decades sooner.

Sure, you lose more water to evaporation, but so what? Either install a ATO, or just do like I still do to this day and just check and top it off as needed.