Need some clarification on RO/DI water

[vromanowski]

So far I've been using tap water but I've been reading about RO/DI water and most sources say it's much better. However I've read a few articles that say RO/DI water is also too pure and fish+plants suffer from missing important nutrients found in tap water.
Therefor, if you're going to use RO/DI is it best to use a mixture of it with some tap water and find the right balance of the two for pH, gH, etc?

How do you guys use it?

Also, when water evaporates in your tank, only pure water is evaporating right? so when doing "top offs" are you supposed to use only RO/DI to keep the tanks' water chemistry the same?

As of now I can't really afford to throw down 100-150 on a unit, so does anyone reccomend a brand/type of bottled water that is a good substitute until I can afford my own system?

 

[mfdrookie516]

for a freshwater aquarium, tap is way better unless its got alot of bad stuff in it (copper, ammonia, nitrates). RO/DI water has no buffering capacity and will cause a yo-yo-ing ph if appropriate buffers are not put in. Now the water that comes from the waste line of the ro/di unit is fine for freshwater, and is what most people use when they have both fw and sw.

 

[vromanowski]

thankyou for the reply, I'm considering trying out a saltwater tank in the future too (~6 months), so I'd still like answers to those questions. sorry if i put this in the wrong forum

 

[mfdrookie516]

If you have a sw tank, ro/di is the best. Not necessary for a FOWLR, but if you want corals, then ro/di is the only way to go. You can use the ro/di water for the sw tank and the waste water for the fw tank...

 

[vromanowski]

Is the DI necessary? I went to my LFS and talked to the the owner for a bit, he said he used RO water but he said the DI stage isn't necessary for sw/coral, but I'd like to know for sure

 

[cabezon]

thanks for the good idea. now I dont have to plumb my waste water, I can just put it into a 5 gallon jar for use in the FW.

 

[ezy33]

Phosates

Is the DI necessary? I went to my LFS and talked to the the owner for a bit, he said he used RO water but he said the DI stage isn't necessary for sw/coral, but I'd like to know for sure

IME If your water supply has any phosphates, then you'll need a DI filter to keep algae at bay.

 

[vromanowski]

good to know thankyou

 

[happygirl65]

It is often easier to just use tap water, if you do yuse RO/DI then mix it for sure. Test your water for phosphates...even if your tap water doesnt have it, you will have some from dissolved organics in the tank. More phosphates will make it necessary for more water changes but you don't necissarily have to use DI water.