What do you guys add to RO water?

[gex18]

I have a Juwel Rio 400 with several discus anbd other inhabitants, however my pH is a 5 - 5.5 at the moment (according to JBL ph meter), but when i add water (2 x 10% changes a week - is this enough) the ph increases to 6.5 - 7, so am thinking that these major ph fluctuations are contributing to the stress of the discus, and as i understand i need to aim for a GH and KH of 6 each, to maintain the ph over a longer period, so was wondering what you guys use as an additive for your RO water to acheive this?

Cheers

Anthony

[ozarowana]

Your pH apperas to be dropping due to the lack of carbonates (buffering) in pure RO water. A constantly fluctuating pH will stress the fish.

People usually mix RO water with tap water (or RO waste water). The % of each will vary depending on your tap water.