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RODI Waste Water Comparison to Tap-Water for Freshwater Aquaria?

Being the frugal aquarist I am I was wondering if my RODI waste water could be used for my freshwater aquariums (I have 10 and it would definitely be a convenient use of waste water). So I did some water quality tests to compare it to my tapwater (which I typically dechlorinate and use). Here are the results:


Water ParameterTap-WaterRODI Waste Water
TDS153 ppm175 ppm
pH (API)7.87-7.2
Ammonia (API)0 ppm0 ppm
Nitrate (API)0-5 ppm0-5 ppm
Nitrite (API)0- 0.25 ppm0- 0.25 ppm
Phosphate (Seachem).701.5 ppm
kH (Readsea)~5.3 dKH~5.3 dKH

The ranges were because I couldn't really tell the exact results, in hindsight it might've been a good idea to post pictures of test results. I only ran 1 test for each parameter except for TDS and phosphate where I took an average of 3 tests.

So I have heard people say NOT to use RODI waste water as it has high nitrates and phosphates, but I did not see a real difference in nitrates. The phosphate was doubled, but most freshwater fish have a pretty wide range of tolerability when it comes to water cleanliness and all my tanks are pretty heavily planted or at least have a bunch of hornwort/java moss to absorb excess nutrients. Admittedly before doing a search I did add some waste water to 2 of my aquariums and didn't really notice a difference in my fish;s behavior I think I had some cloudiness but that disappeared pretty quick.

I guess my question is what are your RODI waste water parameters? Anyone ever use it in freshwater aquaria? I think I'm leaning towards using it for freshwater maybe diluted with dechlorinated tap water. I would love to know if i missed something or what your opinions are.
 
I use 100% ro/di waste water for my freshwater planted tank. I have several rare plecos, cardinal tetras and geophagus cichlids and use it with confidence. Never had any issues. In fact I do water changes (simple drain-refill) every time I am making RO/DI water for my reef tank. I do this to not completely waste water by filtering water. The rest goes to water my landscaping outside.
 
I feel key is a planted aquarium. I find my planted tank loves the higher phosphate levels. And plants look better with a nutrient rich water
 
@Jph I'm glad to hear it! I will have to start doing the same, I was surprised to see just how much waste water an rodi system produces without a booster pump.

@Sponge Thats what I was thinking too it sounds like waste water is going to be better for my planted aquariums!
 
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