What to use when topping the tank...

[shilo_1]

After reading many different things, I thought I would come and ask here...

After some tank water evaporates, what do I refill with ? Plain water (not tap, but "clean" water) or pre-mixed saltwater ?

I've read to just add plain water...but wouldn't that drop the salinity ?

[AttackDonut]

What happens is when you lose water through evaporation, the salt remains behind (or most of it anyway, some ends up as "salt creep" on the edges of equipment) and thus the salinity raises. You top off with purified fresh water to return the salinity back to where it should be.

[CIMulation]

"Purified Fresh Water" as in spring water?

[shilo_1]

Ideally....tap water is full of chemicals that are not healthy for your tank... Boy oh boy...the fish tank "drinks" better than I do ! lol

[CIMulation]

So would spring water be ok?

[shilo_1]

I would think so, being that it hasn't been chemically treated.

[yessongs]

RO/DI water

[NicoleC]

"Spring water" is frequently tap water from somewhere else, and highly mineralized at that. If you are going to buy water, some of the water vending machines are RO (check to be sure) or the LFS probably sells it.

[Entropy]

I would use RO water if possible (or RO/DI). You could always use distilled water as well but that could get expensive.

[b0lingball]

Some LFS are selling RO pre-mixed salt water. Should I use that to top off the tank or just plain RO water? Thanks

[jjmg]

For top-off don't use anything with salt added. The salt stays in the tank as the water evaporates. If you don't have ro I'd buy distilled before using spring or drinking water/