Large tanks and evaporation losses

Hey all!!

So if you've seen my threads you know I am planning a large saltwater aquarium, in the range of 10x4x2.5 or 12x4x2.5. It will be a FOWLR tank with a small shark (epaulette), groupers, wrasses, tangs, and rays.

My wife and I made another step towards making this tank a reality - we picked out and met with our custom home builder last night! We are both "green" loving people, and this guy is the top rated green builder in Minnesota, and the one with the most LEED and Challenge certified houses (he built a 3500 sq ft townhouse with 4 people living in it that had a total annual energy (gas + electric) bill under $800, my current townhouse is smaller than that, has less people living in it, and has triple that bill). One big aspect of these houses is being very well sealed and air tight, and being very good with air handling and moisture control. And yes, I know, having 1000 gallons of water going in circles is far from green, and the electric bill alone will be $1000+ / year for the tank, but hey, at least its better than a 1000 gallon tank AND an energy inefficient house?

Well I brought up the large aquarium plan and he immediately was very concerned with the evaporation rate. Since it would be very air tight and moisture controlled, significant evaporation could be extremely bad inside the house. So he wanted an estimate of what it would be. So I have a few questions:

-If I had a 10x4x2.5 aquarium with a tight fitting lid, with a 300 gallon sump in a room behind it with a tight fitting lid, what kind of evaporation could I expect?

-Temperature is going to be a huge driver in evaporation rate, with an epaulette shark, yellow ray, a few groupers (miniatus, blue dot), a few larger wrasses, a few larger tangs, what is the lowest temperature I could go? Most of the species give a range, like 72-80 or 74-82. Is keeping it at 74 alright? Clearly they will grow slower, which is fine by me, but will they be healthy? Will it greatly slow down their activity and make it a dull tank?

-If the tank has a tight fitting lid and the sump has a tight fitting lid, I'm guessing the vast majority of the evaporation is going to be in the skimmer (with tons and tons of air going through it'll come out very humid). Has anyone done anything to try and control this? I don't see a good way to stop evaporation without stopping the function of the skimmer, but what about stopping the evaporated water before it enters your house? Could you either vent the skimmer straight into a dehumidifer or to the outside? I tried searching for this without any success.

Any advice / numbers / suggestions would be very helpful, my various online searches yielded nothing valuable. There are some uncertainties about getting the tank already (due to large upfront and large upkeep costs), and if its going to cause big mold / water damage problems inside the house it could be a large step away from actually making the dream a reality.

Thanks in advance...

The answer I was afraid of - it depends. Any case study examples to start from?

For gas exchange the skimmer likely does the brute of it. I'll likely try to vent that somewhere. If I go that route I could easily seal the aquarium lid and put a fan on one side to sweep fresh air through, and a vent on the other side to duct it to the "somewhere" of the skimmer. I think that would be cheap and easy (and likely better gas exchange since there would be an active flow) so then the question would be where to vent it.


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So I talked to an hvac guy about this and he thinks it's a non issue.

Basically all houses have air turnover to outside, even well sealed ones. So just use the aquarium as your air source. You'd seal the aquarium lid and have a fan blow air through it and out a duct, and then you'd duct the air outlet of the skimmer and vent both of those straight outside ( or though the home heat recovery ventilation system first ).

Any reason this wouldn't work? You'd get all the gas exchange you need, it just would not have the humidity go into the house. I'm also told the size and cost of a dehumidifier and electricity to run it would make this a much easier option, especially if you can design the house to accommodate it.

One question though. Would a sealed sump need gas exchange too? There will be a large refugium in there. Since the plants use co2 and there is plenty of flow I'd imagine you can have it with minimal gas exchange, but another fan wouldn't be hard.


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