RODI waste water use

[schleppey]

Hello, I have some questions about RO unit waste water and figured this is the place to be.

The units "waste" water should be cleaner than my tap water, correct? My tap does not go through a sediment filter or carbon before I use them for my planted tanks. Can I just cut the RO water with a little bit of waste water and have some solid freshwater for my planted tanks?

I usually use my softened tap which has been trash for my planted tanks. My RODI station is the only sink in my home running unsoftened water. I recently was wondering if I could just use the ro/waste water mix which would have a much better mineralization and will be much more consistent that city tap. Also it will be slightly filtered from the sediment/carbon filters in the RODI unit. Seems obvious enough to me, I was just wondering if you guys have experience doing something like this and was looking for some verification.

 

[LadyMac]

Good question. I was always told it’s more of a concentration of minerals since the good part of the water is kept. Kinda like, a gallon of water, sent through an RO filter would give you say, a quarter of good clean water and three quarters of the minerals and such. People do use it for watering plants so perhaps a planted tank could benefit if just a little.

 

[Crossfire]

Waste water has a pretty high TDS, but if it's for a planted tank and you added something like seachem prime it should be okay if you don't mind adding it.

I checked my TDS waste water once and it was pretty much just as high as the tap water going into the unit. A lot of people use tap water with a de chlorinator for fresh water tanks, so it's not bad but isn't the best option.

 

[LobsterOfJustice]

RODI waste water is perfectly fine to use for a freshwater tank. It will have slightly higher amounts of dissolved minerals but freshwater inhabitants generally don’t mind.

 

[redfishbluefish]

@LobsterOfJustice got it! Unless you live in certain areas of the country where you almost need to chew your water (ie certain areas of Arizona come to mind, over 1000 TDS), you'll be just fine using in a freshwater tank. It's already been dechlorinated!

 

[Peace River]

I use a conductivity meter with my water for FW - this would quickly show you the difference between the RO waste water and the tank water. Good luck!

 

[schleppey]

Thanks everyone, I will test the TDS and move from there. If I remember correctly last time I tested the waste it was ~550 TDS so I should be good to go

 

[Daniel@R2R]

Thanks everyone, I will test the TDS and move from there. If I remember correctly last time I tested the waste it was ~550 TDS so I should be good to go

550?? That seems high. Is that kind of the norm for freshwater tanks? I've only ever kept saltwater.

 

[schleppey]

550?? That seems high. Is that kind of the norm for freshwater tanks? I've only ever kept saltwater.

You are right, it is a little high but that's just more minerals for the plants, the fish won't mind. Freshwater fish are absolute tanks at adapting to stable conditions. I would be a little worried if I was in the 800-1000 range but with 550 almost all fish will be golden. The cutoff between "hard" and "soft' is around 300-350 tds so I'm still in the money barring extremely picky species. Quite a few breeders of discus and other south american species just use their hard tap water because it's easier and the fish will acclimate to home aquariums better. I would always prefer having harder tap because its pretty easy to cut with RO water so Im happy with 550