RO/DI wastewater for a planted tank

[Jasonv]

Hi. Has anybody ever use the wastewater from a RO/DI for a planted tank? 

[Sykes]

I haven't, but don't see why you couldn't. As I understand it, the waste water is basically the same as your tap water except everything is in higher concentrations. Actually tempted to try it now to cut down on my water waste (though simply changing less water is far more effective for that).

[Andy's Fish Den]

I have not tried it myself, but I have heard of people using it in their African cichlid tanks.

[Nataku]

Well not quite in a planted tank, but in a garden, sure.

Story time!

So in central Florida, public drinking water is pulled from our underground aquifers, run through filtration (to various degrees in different municipalities) and then off to the pipes it goes. One central Florida county which a family member worked for for a number of years back in the 80s-00s, had a big tank in the front of their main office at their largest water plant. Some eight feet long, I don't recall how deep or wide. But it was fed entirely by the water pulled up and processed there at the plant - no declorinator used. Just water that had been pulled from the aquifer, and run through the skids (think of these as ginormous, industrial RO/DI systems), and then they had two lines - one the filtered water, which went to the fish tank, and the other the 'wash' line as it was called, which was the 'waste' from the filtration that ran to a bed of roses. Those roses were practically hedges. So I think they liked the 'waste' water.

 The fish tank held a group of oscars that had been pulled out of local waterways and been put in the tank (oscars have  been an invasive species in Florida for many years). They  got very large, as oscar do, and bred. Once a year they held a picnic for the utility workers - one of the popular things was a fish fry, where they pulled the largest oscars out of the tank and fried em up. They were delicious. There was always so many babies there were plenty to eat the next year.

[Ryan W]

Seems like a backwards process to me. I suppose you'd have to consider the reason why you got the RO/DI unit to begin with and that if reintroducing those filtered compounds back into your tank (at a much more highly concentrated level) is really the best thing to do.

What you could do is use regular tap water to cut your RO/DI water with so you aren't creating as much waste water to begin with. If you can afford to cut it with 50% tap, you just cut your waste water in half too.