Water for Top Offs (from Evaporation)

having open topped tanks i use the evap line to time my water changes it takes a week to drop half an inch below the rim and its time to change.. i do 50% weekly usually on sunday afternoon
 
what is the best source for DI water? I have a 100g and probably lose about 12g a week. my GH is already a little higher than i want, and i intend on raising my KH to keep my pH more steady. If I raise my KH, my GH will be even higher, so I'm thinking I don't have any choice except to use DI/RO/Distilled for evap, and even mixing it in with the tap for water changes. How do you source the DI? I'm really not interested in buying 10-15g a week from the store.

Hebily said:
If you have any evap, the remaining tank water is higher concentration of everything non-volatile. So, say you have a gal/week loss, and do 3 gal water change. You pull out two gal of higher conc water. The remaining water is still higher conc. You add three gal of normal conc water, diluting the conc in the tank. The tank concentration of non-volatiles is still slightly higher than before. You want SOME mineral content in the tank, this is good for the fish... too high is bad. Also, Cl- is non-volatile. If you properly use dechlor, this shouldn't be a prob, but if there is any chlorine in your water those trace amounts will build up over time. Because of these, and other potentially dangerous non-volatile chemicals, it is good practice to add some DI periodically, depending on your evap rate. However, you should not add only DI, unless you add other things to replace the missing minerals, ions and the like. In theory, all evaporated water is DI (assuming no entrainment, which is not the case) and should be replaced with DI. It can get pretty tricky... Just keep an eye on General Hardness and Total Dissolved Solids over time, and if either goes up too much, add some DI to bring it back to normal. It won't take a lot, relative to the size of the tank. Most of us don't have enough evap to have to worry about this for years... it also depends on the quality of water used in changes....
Click to expand...
 
get a RO/ DI filter
 
Can't really help you there... honestly, I would probably shell out the money for a small RO unit... but remember, what are your units for your GH? PPB? even PPM, how much DI at 0PPM would it take to reduce the PPM of your 100gal tank to where you want it? I would guess that it's no where near as high as you think... I'm not really good with applied chem, though... just basic theory... just guessing, out of 12gpw evap, i would expect to replace less than a gallon with DI. Like I said, that is a very rough estimate... there are alot of factors involved...
 
do to the ammendment of the reply I was replying to, this post is no longer valid. although, technically neither an RO or a IX would be a filter....
 
basically pure water out (due to evap loss) pure water back in RO, DI or distilled (tho is is usually recommended to aerate distilled water.)

;)
 
Star's right... if you replace exactly the amount lost to evap with RO water, it would not cause a quick depletion minerals... and if GH gets too low, you can just do a replacement or two with dechlorinated tap water and that should bring it back... I would definately get an RO, if I were you. That keeps everything alot simpler.... There are different membrane grades, for different purities, so watch out for that...
 
You must log in or register to reply here.
AquariaCentral.com
Top Bottom