Just curious

[markyrich]

I started keeping fowlr tanks 35 years ago. I hate to tell everyone (hung up on 0 tds) but there was no such thing as rodi water. I used what I had, I later found out my in was about 300 tds. I seldom had any problems. I do have a good rodi system now but it will only stay at zero for a few weeks.then goes up to 10 or so. I'm not worrying about it. I have a few soft corals and mostly fish. Maybe it makes a big difference with difficult corals.

 

[ISpeakForTheSeas]

Maybe it makes a big difference with difficult corals.

The point of RODI systems in the hobby is really just to ensure no toxins (like copper, for example) get brought in with the water for the tank no matter the source.

Tap water is totally fine to use in some places/on some wells but it would kill at least the corals and inverts in other places/on other wells. Additionally, the quality of the water can shift over time - so water that was fine may suddenly change and starting poisoning things, or water that was terrible may suddenly be useable.

So, RODI isn't always needed, but most people use it to guarantee their water won't doom their tank.
https://www.reef2reef.com/threads/h...-water-vs-rodi-water-for-a-reef-tank.1022817/

 

[markyrich]

Understood, and that makes sense. I'm more responding to a lot of these reefers who are hung up on the (0) TDS. I've read a lot of them making statements that if it's 3 TDS get rid of it. That to me sounds ludicrous. I can't be the only one I have 2 different RODI units one has 7 stages and the other 4. After changing everything out I will stay at 0 for a couple weeks then it starts creeping up.

 

[ISpeakForTheSeas]

Understood, and that makes sense. I'm more responding to a lot of these reefers who are hung up on the (0) TDS. I've read a lot of them making statements that if it's 3 TDS get rid of it. That to me sounds ludicrous. I can't be the only one I have 2 different RODI units one has 7 stages and the other 4. After changing everything out I will stay at 0 for a couple weeks then it starts creeping up.

Yeah, low TDS generally isn't a cause for concern (though it potentially could be depending in what's getting through) - IMO it should generally just be an indicator that it's time to replace part of the filtration.

If you're getting TDS creep that fast, I'd look/ask around on the forum why - I know there was a thread awhile ago about burning through DI resins super fast and degassing the water to slow the resin consumption down; you might look into stuff like that to see if something's going on with your water that's messing with your filtration.

Again, though, I wouldn't expect issues from low TDS, so I don't think you'd have anything to worry about.

 

[Randy Holmes-Farley Verified Community Expert]

Understood, and that makes sense. I'm more responding to a lot of these reefers who are hung up on the (0) TDS. I've read a lot of them making statements that if it's 3 TDS get rid of it. That to me sounds ludicrous. I can't be the only one I have 2 different RODI units one has 7 stages and the other 4. After changing everything out I will stay at 0 for a couple weeks then it starts creeping up.

Not sure why you believe it is ludicrous, but I’m glad your tap water was acceptable. Not all tap water is acceptable, and 0 ppm tds ensures that the water is fine.