RO/DI for brackish

[reiverix]

I got myself a 75g per day RO/DI unit for my reef. Works like a charm so I'm wondering how safe it is to use the water for my brackish tank? Would I need to add any buffers like RO Right or does the salt mix get the water just right.

My tapwater is very high in phosphates with the occasional nitrate spike after serious rain and my brackish tank is the only one without plants. I change 50% water each week but since I have have access to pure water would it make sense to use it?

[RTR]

You likely will need to do additional buffering at low and middle BW ranges. Equilibrium will help, but monitor to be sure.

[reiverix]

I have some Osmo Prep laying around. Think it'll work?

[tekknoschtev]

I have been under the impression (and tested myself) that RODI water does not need to be buffered when mixed with decent quality salt because RODI water has little to no buffering capabilities in and of itself (ie. if you add a gallon of RODI water to 10gal of salt/brackish water, it wont effect things too much). At least this is how I understand it for pH. I dont know what else you would be buffering, however, RODI water has no pH buffering capabilities.

[RTR]

The need for buffering is entirely dependent on the density of the water. At low-end BW, IME RO + marine mix needs buffering, especially for puffers. There is lot of difference between adding a gallon of RO to 10 gallons of SW or high end BW and making up low-density water to support high bio-load fish. Try it your way and let me you KH/pH drop between partials.

[Pufferpunk]

Too bad that won't work, cause I'm having a heck of a time w/long hair algae in my F8 tank!

[Raphael]

I had the same problem in my F8 tank and I got rid of it with interpet hair algae remover.

[RTR]

It is not that RO or RODI won't work, it can and will. But at low densities with high bioload fish, you are likely to need more buffering or you may get detectable pH/KH decline within a week. TDS will stay fairly stable, but alkalinity burns to some degree.

Many moons ago, before Equilibrium and RO Right were around and I had started playing with F-8s, that was the whole impetus for me to play w/OE-RFUG. Blame it all on my trying to maintain high pH (read as: high KH), for low density BW w/F-8s. Setting so many F-8 tanks allowed me to run lots of test setups to hone the technique.