tds reading and water changes

[MikeEe]

Ive been using only R/O water for the last 2 years to top off my water and do water changes. Ive never tested the TDS reading of it until this weekend. It was in the mid-20's. What are the effects of using water with this reading? My colors are okay, but I do have a few brown corals that have never colored up. Ive replaced my old unit and got a r/O DI unit and the reading is 0.00.

As for water changes, would it be better to do a large 10 percent water change weekly or 5 percent twice a week. Thanks guys

[ReefWreak]

I've been using 20tds water for topoff for a year now, since I've had it, and have run across no problems other than some VERY slight algae issues that are more related to overfeeding. I also use NSW from the LFS to do my water changes (which I havn't done one in months) so maybe that's why I havn't had issues with it?

5% twice a week is technically removing less of the original water than one 10% weekly, however you're going to have more stability and nutrient replenishment if you do 5% twice a week. Maybe do 7% twice a week and figure out the statistical breakdown of the nutrients removed over time.

[Serioussnaps]

its time to change out your filters man

[Randy1]

If your using just ro you may only get it down to 7 or 8 with new filters depending on your tap water. I had to add a DI filter to get it to 0.

[ReefWreak]

The filters that I'm using are only about 2 months old, and it's just a Micron-RO-Carbon filter, maybe that's why. And we get tons of Iron and calcium in the water here in FL so that could cause it too.

[SeanT]

It was good that you got your TDS to 0.
IME, larger waterchanges, in excess of 20%, are best.
Just make sure to match salinity, temp etc. before starting your return, I assume you have a sump, and all should be fine.

But of the two choices you proffered, I would go with the 10% once a week over the 5% twic a week.
jmo.

Sean