# Evaporation



## gmachine19 (Apr 21, 2010)

So I currently have a 10 gal tank for growing out some baby jaguars(thanks nemo!) I have it for almost 2 weeks now and I noticed that the water level just dropped dramatically over 2 weeks.

Setup:
10 Gallon tank NO COVER
150 watt stealth heater
Sponge filter

Is it normal for it to drop 1/4 of the level in 2 weeks? I didn't add or remove any water and I'm pretty sure the tank has no leak. It there was a leak, the newspaper its sitting on should be wet by now...


----------



## 2wheelsx2 (Apr 21, 2010)

What's your room temp and the tank temp? Evaporation would be partially a function of that differential. The other would be surface area and since you're using a sponge filter, you're creating more surface area turnover from the bubbles breaking the surface. I can tell you that in my 100 gallon cube that I lose 2 to 3 inches of water a week so that's like 10 gallons or more, since I hold the temps at 29C. Put a cover on the tank if you don't want to lose so much water.


----------



## effox (Apr 21, 2010)

Yep, that's normal. It's quite annoying actually, especially with a salt water tank.


----------



## Diztrbd1 (Apr 21, 2010)

agree with Gary & Chris, every one of my tanks covered or not, lose an inch every couple of days. The temp in my apartment is not warm at all. In my 10g which is covered and has a HOB filter, it loses about 1/2" a day to evaporation. I did a wc Friday in it and it's down approx. 2" now. So in 2 weeks, if I didn't top it off every few days, I would probably be down to the same level you are. Covering it will definitely help to retain some of the water.


----------



## gmachine19 (Apr 21, 2010)

I see. I have experienced evaporation before but not this much. My room temp is around 22c and my tank is 28c


----------



## 2wheelsx2 (Apr 21, 2010)

gmachine19 said:


> I see. I have experienced evaporation before but not this much. My room temp is around 22c and my tank is 28c


That's your culprit right there. The big differential is causing more evaporation. If your room temp and tank temps were closing there'd be less evaporation.


----------



## gmachine19 (Apr 21, 2010)

Thanks for the info fellas. Now I can rest assured that I don't have a leak


----------



## Jonney_boy (Apr 28, 2010)

Agreed... I have a "huge" temp difference in my rooms... i keep the house cool @ 16-18 as it's downstairs and my tanks warm (30-31 for discus)... I loose almost 1" a day on a 100g cube tank.

A cover defently helps tho, few other tanks are covered and loose MUCH less water. I had a 10 gal that was covered and now is open top... Will loose at least 3x more water open top.


----------



## joker1535 (May 23, 2010)

I dont mind it all all. Ive got an open 135. Means i have to take less water out for my weekly wc.


----------



## kelownaguy (Jan 1, 2011)

2wheelsx2 said:


> That's your culprit right there. The big differential is causing more evaporation. If your room temp and tank temps were closing there'd be less evaporation.


So if the room was warmed to 28 evaporation would be less?
I don`t think so.


----------



## 2wheelsx2 (Apr 21, 2010)

kelownaguy said:


> So if the room was warmed to 28 evaporation would be less?
> I don`t think so.


You don't have to take my word on it. It's the internet after all, and most people have taken science courses. Keep a bowl of water in your basement and one in your kitchen and measure water levels tonight and then in 7 days and post back to this thread.


----------



## kelownaguy (Jan 1, 2011)

That wouldn`t mean much.
Humidity and airflow would not be the same.


"The amount of water evaporated from a body of water in contact with circulating air can be calculated with the following equation:

E = k V A (xs - x)

Where:
E = amount of evaporated water (kg/h)
k = (25 + 19 v) = evaporation coefficient (kg/m2h) 
v = velocity of air above the water surface (m/s)
A = water surface area (m2)
xs = humidity ratio in saturated air at the same temperature as the water surface (kg/kg)
x = humidity ratio in the air (kg/kg)"

Consider a 27 degree aquarium in a 32 degree room w/a chiller that lowers the temp to 25.
Clearly,xs will decrease as will the evaporation rate.
The air/water temp difference has incresed but the evaporation rate hasn`t.

Now consider the 22 degree room at 25% RH w/a 28 degree aquarium.
Raise the room temp to 28.
In this case,evaporation rate does indeed decrease.(Ya larn somthin every day.)
I make it a massive 0.42% difference,but,what do I know?
Pretty trivial and hardly worthy of mention,IMO.


----------



## 2wheelsx2 (Apr 21, 2010)

How about accounting for the convective properties of the differential of the water/air interface and the turnover of the temperature differential. Increased surface area due to the water flow at the surface and the increase effective surface. Those aren't trivial I don't think. Also the different volatilities with variance in dissolved solids? Also the fact that the humidity and temps are in transition at the water interface. Sounds like a pretty interesting project, since you seem to be into those sorts of things. I haven't cracked open my engineering books for 25 years now, so maybe they're teaching more than they taught me at UBC.


----------



## tang daddy (Apr 21, 2010)

If you have a sponge filter in the tank, there will be alot of evaporation.... As the bubbles pop, water is evaporating into the air. My open top 30g with an air stone in one corner goes through 1/2 a gallon per day. My other 10g with 2 aquaclear hob goes through 1/2 a gallon per day aswell. The more surface agitation the more evaporation... My 75g reef all open goes through 30g every 2 weeks. The temperature helps the water evaporate even faster, a completely sealed tank won't evaporate a drop!


----------



## kelownaguy (Jan 1, 2011)

2wheelsx2 said:


> How about accounting for the convective properties of the differential of the water/air interface and the turnover of the temperature differential. Increased surface area due to the water flow at the surface and the increase effective surface. Those aren't trivial I don't think. Also the different volatilities with variance in dissolved solids? Also the fact that the humidity and temps are in transition at the water interface. Sounds like a pretty interesting project, since you seem to be into those sorts of things. I haven't cracked open my engineering books for 25 years now, so maybe they're teaching more than they taught me at UBC.


Gone all scientific all of a sudden.LOL.
The things you mention are even more trivial than the major factors.

"How about accounting for the convective properties of the differential of the water/air interface and the turnover of the temperature differential. Increased surface area due to the water flow at the surface and the increase effective surface"

Any aquarium will already have enough water movement to drown out convective effects.
I don`t have enough decimal points to express how trivial that is.

"Also the different volatilities with variance in dissolved solids?"

Consider an aquarium w/an intial TDS of 200ppm that loses 10% to evaporation.
Evaporation rate now decreases by a whopping 0.002%!
More triviality.

You should open those books once in a while.


----------



## gmachine19 (Apr 21, 2010)

U guys lost me at convective LOL!


----------



## Mferko (Jun 8, 2010)

put a glass top on your tank problem solved, no fish jerky on the floor and evaporation reduced significantly


----------



## gmachine19 (Apr 21, 2010)

So far no fish jerky yet lol. I already placed one. And evaporation seemed to be lessened.


----------



## Mferko (Jun 8, 2010)

i lost one of my favorite acei to him jumping out the back 
found him a month later dried up under the tank


----------



## Morainy (Apr 21, 2010)

Charles (Canadian Aquatics) makes glass tops for tanks. I only found that out a couple of months ago and before that, I always wondered where everyone got their glass tops from. If your tank is mostly uncovered, you can see if Charles will make you a top. 

HOB filters also cause evaporation, especially if you leave their lids off (as I do -- I have a habit of dropping them down the back of the tank and stand...)


----------



## katienaha (May 9, 2010)

I generally lose about 3 gallons every 3-4 days in my 55g tank to evaporation. It goes faster once the outflow of the filter starts to break the water surface. Open top, hot lights shining on it 12 hours a day, dry house... it all contributes. Just remember, if your water is hard like mine, you can't just do a top-up. You will have to remove water and then top up, as the hardness of the water in the tank will just continue to increase.


----------

