# Can evaporation be my weekly water change?



## Drifty (Nov 28, 2006)

I know this sounds weird but since i have a 10 gal open top, the water evaporates quite quickly. Every 2 days its about a cm or 2 below the black part of the top. When i see this i add new water back up to the top of the black part. Can this count as my weekly water change?


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## mahamotorworks (Nov 7, 2006)

Nope.
When Water evaporates it leave behind the stuff you take out when you do a water change. In a SW tank youhave to really look after it or it will raise the Salt level to high and kill/harm your fish. 

Nothing will replace the water change.

MAHA


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## epicfish (Sep 11, 2006)

Yep, just like mahamotorworks said, your TDS (total dissolved solids) will rise and NOT be good for your fish and plants.


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## Drifty (Nov 28, 2006)

ok thanks


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## ed seeley (Dec 1, 2006)

You will actually need to keep a MORE careful eye on your water and possibly even change more water!

The reason I say this is that as water evaporates, as everyone has said so far, just the water is evaporating, leaving dissolved solids behind and then if you are topping up with tap water (that contains more dissolved solids in it) you are increasing the TDS over the periods in between water changes, changing the conditions in the tank. If you leave water changes too long it could be bad, as epicfish said.

Ideally top up with pure RO water (which has very very low, or zero TDS), or make fairly large water changes every week.


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## Jimbo205 (Feb 2, 2006)

Drifty, two suggestions. One you will thank me for, the second you will eventually appreciate so much you will name all your boys after me. 

One - get a glass top for your tank. Not to keep your fish from jumping out. (Stupid fish deserve what they get.) But just for this reason - to keep the water from evaporating. Although being in tropical warm Florida you may not have the same issues with dry air in the frigid winter as we do up north. But the glass top will probably protect your light fixture pretty well. Here up north the warm water evaporates very quickly in the dry cold air during the wintertime here. 

Second - as fast as you can. Buy Diana Walstad's book - Ecology of the Planted Aquarium on Amazon.com . There used to be a link at the top of the page on this website to purchase it. If you can find that on APC, buy it now. FANTASTIC BOOK - GREAT PRICE. You will read it over, and over, and over, and over again. And it will give you better answers and things to think about than you could ever imagine with your tank(s). On such things as water changes, etc. 

Good luck. 

And if you don't want to buy the book right this very moment, you can get a taste of the tip of the 'iceburg' over in the El Naturale section. When you get exhausted of high maintenance, you will switch eventually anyway.


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## JanS (Apr 14, 2004)

mahamotorworks said:


> Nope.
> When Water evaporates it leave behind the stuff you take out when you do a water change. In a SW tank youhave to really look after it or it will raise the Salt level to high and kill/harm your fish.
> 
> Nothing will replace the water change.





epicfish said:


> Yep, just like mahamotorworks said, your TDS (total dissolved solids) will rise and NOT be good for your fish and plants.





ed seeley said:


> You will actually need to keep a MORE careful eye on your water and possibly even change more water!
> 
> The reason I say this is that as water evaporates, as everyone has said so far, just the water is evaporating, leaving dissolved solids behind and then if you are topping up with tap water (that contains more dissolved solids in it) you are increasing the TDS over the periods in between water changes, changing the conditions in the tank. If you leave water changes too long it could be bad, as epicfish said.
> 
> Ideally top up with pure RO water (which has very very low, or zero TDS), or make fairly large water changes every week.


I agree with all of the above statements. The TDS that are left behind after evaporation can really build up, as can nitrates, hardness, etc., so the only thing that can bring them back into the correct levels is to do those water changes.

I agree with the salt water analogy as well. An employee at our LFS who didn't know better was topping off the tanks with more salt water as they evaporated and they lost a whole tank of expensive fish and corals because the SG became lethally high.

And as Jimbo suggested, adding a canopy will greatly reduce the amount of evaporation you get in the winter.


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