Question on water change

[eugenecj]

hi guys need some advice on water change.
Fact is that water always evaporate and for those who are budget like me, will get a fan rather than a chiller so evaporate rate is even faster so question is, everyone is recommending to change 10%-15% so question is 10%-15% from the initial water line or the after evaporate rate?

Because.. If I take out 10%, adding in those water that evaporate could be more than 10%.
Thanks for the advice!

[Berny]

for marine, usually they top up to regular line before evaporation before water change, that way, they can keep the water perimeter stable. If you're keeping sensitive livestock, i would suggest that you follow the marine guideline

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[mUAr_cHEe]

Water change ratio is to your original water level. Think of it as you will refer to your tank as a '20 litre' tank rather than a '19.5 litre plus minus 500ml' tank.

[eugenecj]

Got It guys. Thanks! So it doesn't matter if I only draw a bit of water out to conclude my 15% water from original water level right?

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[technotango]

Just draw a line of the original water level and add back to the same level. You now have the exact same concentration of NO3 as before the water evaporation. From there, you can change whichever amount that you wish to.

[eugenecj]

Just draw a line of the original water level and add back to the same level. You now have the exact same concentration of NO3 as before the water evaporation. From there, you can change whichever amount that you wish to.

Bro meaning as long as the water added In is the same as the initial water level, it's correct?

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[Urban Aquaria]

Topping up of evaporated water is not considered part of water change, as evaporation still leaves behind all the nitrates and accumulated dissolved waste material.

So for example if your tank water decrease due to evaporation and you want to do 20% water change, just top up first back to original level, then do the 20% water change.

Alternatively just remove 20%, then directly refill whatever amount required back to the original water level, save all the repeated removing and refilling.