Question on water change

[wasabi8888]

I have a 2ft tank with a fan on 24 hours a day. Although there is water evaporation, i do not typically top up the water until the day i do a WC.

Assuming water evaporates by 10%, when i do a 25% water change, do I consider that 10% that evaporated, which means I pump out just 15% of water?

[diki]

Personally, I would consider how high you want the water level to be first, since usually we consider the volume of the water in the tank. If your fishes are ok, should be fine.

For me, I usually top up since the outlet pipe is rather high and I want to control the splashing effect to keep more CO2 in my low tech tank 2 ft tank.

[GIN]

Should do a try and error if the fish have no problem then which U use is not a problem.

[bossteck]

Personally, I think if you want to do a 25% change, then it should be 25% of the water left in your tank.

Reason for this is that during evaporation, all the dissolved minerals/fish waste etc are not removed from the water.

It is just like, if you let a salt solution evaporate, then fill up water to the same level, the solution would remain just as salty. (Just an analogy, not chemistry class )

[wasabi8888]

Bossteck

That's what I think too.. but i read in some posts that water evaporation is like water change....just top up can already....

[diki]

Bossteck

That's what I think too.. but i read in some posts that water evaporation is like water change....just top up can already....

I think it is more to maintain the water condition of the tanks but definitely not the same as water change. I would think those are likely be planted tanks as fish tanks is quite impossible to keep without water change. Plants helps to remove those harmful waste byproducts. Other than that, they are just making their tanks no maintenace tanks!!!

[kemp]

i agree with bossteck's reasoning. That's what i'm practising too, disregard the water lost due to evaporation, still change the desired water quantity that i want

[wasabi8888]

Thanks guys.. make sense to me