Reusing the aquarium wastewater?

[Lantz]

ive been rolling around in my head what could be done to make the water that gets dumped from a water change usable, for say, plants. just seems like it should be good fertilizer for something if there was a way to reduce the salinity without too much work. anyone out there use their waste water for something? or have any thoughts on how it could be turned into fertilizer?

I’m starting a giant sump system in the basement, mostly to farm frags in the future but for now I’m thinking of using wastewater from the display to feed a refugium and see if I can get that water back to zero nitrate then add nutrients and return it back to the display. Haven’t tried it but that’s the theory I’m working towards

 

[alabella1]

Depends on the water volume, a good use is to use it for growing other things like copepods, phyto or hatching brineshrimp. However you do need to sterilize it for use to grow phyto which you can either heat or use a little chlorine.

I love this idea to use it for my phyto. We you talking about the rejected RODI or WC water though? I've been having issues with my phyto cultures as of late so I was going to start sterilizing anyway but this sounded like a great way to cut down on some waste.

 

[Randy Holmes-Farley Verified Community Expert]

I’m starting a giant sump system in the basement, mostly to farm frags in the future but for now I’m thinking of using wastewater from the display to feed a refugium and see if I can get that water back to zero nitrate then add nutrients and return it back to the display. Haven’t tried it but that’s the theory I’m working towards

I personally would not do that. A main benefit of water changes is to remove things you cannot measure, such as organic toxins. Those will still be there.

It also removes the benefit of driving everything in the direction of the starting salt mix. Potassium and a host of other ingredients.

 

[JustOneMore]

I have big 250 gallon totes and use it in the winter when I have icy spots in the driveway. I used about 200 gallons last winter.

That’s what I had planned to do with mine. Glad to read that my collection plan wasn’t a fool’s errand.

 

[Jmas4]

Very interesting discussion! Reusing water change wastewater outright might not be the best idea. As @Randy Holmes-Farley mentioned used water might have elevated chemicals you cant measure and depleted trace elements you cant measure. And repeated putting it back in the tank despite efforts to remove toxins and replete elements may still result in imbalance and not to mention time consuming.

But that doesnt mean you cant maximize efficiency. My sps and lps dominated reef is maintained via calcium reactor and water changes (for trace elements). And nitrates and phos is negligible. This means the wastewater is still useable. I see no reason to use this water for a frag tank or softy or even a fowlr setup. Or even a domino effect where you use waste reef water to change a frag tank, and use used frag tank water (which is now depleted in minerals) to change a soft coral set up (which is less picky) and finally to fowlr setup where fish do not care at all. And it finally gets dumped in the driveway to kill weeds.

(Of course considering all systems don't have high levels of nitrates and phos)

So you don't reuse the water indefinitely, but hypothetically a 20 gallon water change can result in 40, 60 or even 80 gallons of water moved overall. As long as we consider what elements get depleted and toxins accumulated and move it around accordingly.