Evaporation

[VanDogh]

I have heard different takes on this so I am curious as to what you guys think. 

Do you think it's problematic to fill tanks with new water when it evaporates? I have heard some people saying you should not do this and just do a waterchange instead of refilling with water, because the concentration of minerals, especially salt, gets higher.

[Tony s]

On 9/17/2024 at 11:27 PM, VanDogh said:

Do you think it's problematic to fill tanks with new water when it evaporates

Top offs are not a big deal. Assuming that eventually you actually do a regular water change. But I can see a problem if all you do is top off for 6 months without a water change. 

[Silverback]

I agree with Tony.  For fresh water tanks topping off with fresh water is perfectly fine.  Fish and live plants do absorb minerals and salts from the water.  Now if you have  brackish or saltwater tank you would want to replace evaporated water with fresh water instead of saltwater.  As water evaporates in a brackish or saltwater tank the salinity will increase and topping off with saltwater instead of freshwater would in the long run cause the salinity to continue to rise.  

[VanDogh]

Interesting! I did not know that fish absorbed salt. Is this fine for more sensitive species too, like discus or german blue rams?

[Tony s]

On 9/18/2024 at 12:24 AM, VanDogh said:

Is this fine for more sensitive species too, like discus or german blue rams

Tops will still work. But you’re going to be doing a lot of water changes anyway. Got to keep the nitrates down to less than 5 and the water crystal clear 

[face]

It also depends on how hard your water is if you have 100 ppm and you lose 10%that’s only 10ppm if you have 500 that’s 50ppm and it’s not normal a problem because the fish adapt to the slow changes but then if you do a big water change they get shocked and for stuff like discus you’ll likely never find out lol they will have problems before minerals ever build up

[VanDogh]

I see! I am currently on vacation but I will measure my hardness when I come home, I am fairly certain I have pretty hard water. Doesn't the volume of the tank play in as well, due to smaller tanks fluctuating easier? 

Also, how can walstead methods work when they never do any water change but the water must evaporate because it happens to all tanks?

[Lynaea]

If you top up with distilled or RO/DI water they are mineral free so nothing builds up. It’s only when topping up with tap water that issues can occur.   I have no idea how Walstead tanks work.