Is it possible to minimize evaporation?


New member
I'm in the process of building the stand for what will be my first reef tank. I'm planning a 75 with sump, skimmer etc...and I was wondering if it is possible to seal the system to the extent that evaporation will me minimal. The people at my lfs say that I'll need to add a gal per day due to evaporation. If that's the case then I'll never be able to take a vacation again and my wife, who is from europe (they like long vacations) will never let me set this tank up. I was planning a top off system as well, but I know that is not a "miracle cure" for evaporation. I have friends who would be able to tend to the tank when I'm gone but asking them to come over everyday might be pushing it.



New member
you don't have to add water every single day, I used to have a 75g and I added water every three days. As for vacations, you must have someone attend to your tank if you are going to be away for more than a week. I have a house sitter that I have trained on the basics of my 180...
Where in KY are you located?


New member
The less open the top/refugium, the less evaporation. Also, minimizing airflow over the water surface will lessen evaporation


New member
I live in KY as well. I have a 90 that evaporates 1 - 2 gallons a day. The auto top off will be your best friend. You will still want someone to come over to feed the tank every other day or so but with a nice sized resevoir for the ATO vacations shouldn't be an issue. Without an ATO, you'd better show your buddies how to add water to your tank,. maybe not everyday...


BTW -- To answer your question Look at the previous post from loachmaniac. I think you would be happier, and your tank as well, with a more long term solution like ATO. Just my opinion. :)


Staff member
RC Mod
If you can set up an adjacent buffet or armoire, you will have both nice furniture AND plenty of room for a topoff reservoir.

I have left a gallon-a-day evaporating 54g for two weeks by leaving, close to my rig, several additional buckets of ro/di, with the instructions to my tank-sitter to check the reservoir after 5 days and be prepared to add water via a maxijet pump she could put in a bucket. No muss, no fuss. Empty refill bucket to the kitchen. One bucket left in reserve in case we should be delayed by weather or in case evap rate exceeded expectations. I also checked out my sitter on running the ro/di for refill if things really went haywire.
It can be done in a civilized manner. The adjacent cabinet can also be used for a kalk or calcium system, plus storage of other gear.
If you have a basement, OTOH, drop two lines through the floor and put the whole support rig down there.


New member
my 75g seems to need about 800ml of water a day already. and it doesnt even have the high power lights ( only 2 x t5 ) use an auto-top up. ull probs find that if u * seal * tha cabinet the wood may absorb water to a degree and cause swelling ?


New member
I think an ATO is great. However, I have left my tank for ten days without top off without any problems. I think that evaporation changes the salinity slowly so everything in the tank adapts. Also, salinity doesn't rise as much as you would think because some the salt precipitates out of solution. So don't let top off issues keep you from setting up your tank. Good luck!


Premium Member
The best way to minimize evaporation is to minimize air movement. Plan a canopy and lighting system that generates less heat so you don't have to use cooling fans, that's what makes evaporation take off. In my 250g, I evaporate a little more than a gallon a day. My 30g topoff reservoir is good for almost a month. I have no fans, an open top canopy for passive cooling, and a chiller that's plumbed outdoors.

J. Montgomery

Mouth Pipetting
You can also lower the temperature of your water and increase the humidity in your house to decrease the rate of evaporation. But yeah, expect a good bit of evaporation, it just goes along with having a reef tank.


Recovering Detritophobe
You can minimize evaporation, but will likely have heat problems. I evaporated more than one gallon daily on my old 75. Simple solution: auto topoff.


New member
A chiller will keep more water in the tank, they are nice to have but expensive (to buy and operate). For a 75g, I would get at least a 1/3 HP chiller. I have a 1/10 HP on my 65g--not enough (though it was initially bought for a 30g).


New member
Definitely get an ATO. I have an ATO and all I have to do is refill a 5 gallon bucket every week. And when I go on vacation. I hook up a larger reservoir, so it can go a few week without my sitter needing to worry about that. I think it is well worth the extra $20-30.


New member
yeah your going to need to setup and ATO. covering the display and sump will minimize evaporation, but could cause ph and temp issues.

If i left my tank without topping ff for 10 days i would lose at least 30 gallons of water. my sump would run dry and everything would die. I wouldn't reccomend that to anyone. i doubt many people have enough extra water in their sump to lose 20% of their water with no problems.


New member
Autotopoff! All the better if you can run the RO line straight to the tank. I never topoff by hand. Its my most hated chore.