Poll: Water Filtration Used

[georgiajams]

Just wondering what you use:

[Lifestudent]

100 Gpd R/o Di

[georgiajams]

Also, if you have any practical reasoning for whether you think it helped an algae problem, state that as well.

I use RO only (looking to add DI). I have a very small outbreak of hair algae (patches on a couple rocks) and have problems with Red Cyano despite no nitrates, new lights, and tremendous flow. (BTW, don't turn this into a "how to rid tank of Cyano" thread, as I know all the general wisdom- I'm still experiementing).

From my observations, I have seen some tanks that are thriving in the Atlanta area that use only tap water. No algae problems. Will be interesting to see if it holds up over time though.

I use RO only and, like I said above, I still have some nuisance algae problems from time to time.

[Ray1214]

Here in certain parts of Atlanta, we seemed to be a bit blessed with water quality. I have seen straight out of the tap a TDS reading of 25 PPM. I Larryville it runs closer to 41ppm. From talking to Don last night, compared to other parts of the country, (Oklahoma at something like 412 PPM) it is comparativly good. However I think TDS doesn't always read phosphates since it is organic and not a disolved solid.

Ray

[georgiajams]

Did anyone else think that a reading of 25 for TDS, which the Kent rep said was a good time to replace membranes, seemed high? Especially, when our TDS from the tap seems to be in the 40-50 range. With just RO, I typically get a 0-1 reading on my TDS meter when all is working properly. I was thinking maybe a 4 or 5 would be the right time to replace???

[Lifestudent]

Originally Posted by georgiajams

Did anyone else think that a reading of 25 for TDS, which the Kent rep said was a good time to replace membranes, seemed high? ... I typically get a 0-1 reading on my TDS meter when all is working properly. I was thinking maybe a 4 or 5 would be the right time to replace???

Based on what I've read and the aquarists I hold in high regard, I usually replace something when my TDSs get to 7 or 8.

Bob

[goodfortune]

In the RO/DI thread,http://www.thereeftank.com/forums/sh...ad.php?t=39197, it looked like everyone was getting good TDS numbers right out of the tap, with a few notable exceptions. It may explain why someone living here in Atlanta is able to get away with not running a RO or RO/DI. But to refer to the TDS thread, I'd be interested in how a tap-water reef tank does in the spring!

I think part of the reason we have such good water quality (TDS-wise) is that Atlanta gets most of its potable water supply from surface water sources, namely Lake Lanier and Lake Allatoona. Surface water tends not to have much in the way of dissolved minerals, which contribute to TDS. On the other hand, in places like Oklahoma or Florida, where areas are mostly dependent on well water, I would expect that TDS would be high, due to the minerals dissolved from the limestone (aquifer) that well water is typically drawn from.

The "change filters" set point of 25-50 ppm does seem high, but I imagine it applies to areas where the water tends to be much higher in TDS.

Hope I haven't added to the confusion; just my $0.02

- Michael

[georgiajams]

For someone in the know, or who took good notes last night, if I get 0 TDS after RO, is there ANY benefit to sending that 0 TDS water through a DI stage as well.

Put another way, my question is: what can the DI filter out that the RO filter can not? For example, will phosphates flow through an RO membrane, but not a DI filter?

My impression was that DI just caught anything left over by the RO. For example, if I was getting 2 TDS after RO, the DI would bring that down to 0. But some people thought that TDS didn't tell the whole story, rather that the DI was actually doing more than reducing TDS (but I'm not sure exactly what).

[georgiajams]

However I think TDS doesn't always read phosphates since it is organic and not a disolved solid.

So TDS is just one indicator of water quality. Should we really running more tests on our filtered water to tell if our filters are working properly?

[Stanfill Reef]

The RO will remove the larger dissolved compounds preferentially. Phosphorus is smaller and will pass through. Sodium and chloride (table salt) will pass right through the typical home RO. The DI actually works by exchanging the larger compounds for sodium and chloride. You will always have some TDS in your water, it's just that the typical conductivity meter isn't sensitive enough to read it. If you are worried about phosphorus, you should use DI.

I thought that a few things the Kent rep said were bogus. I would shoot for a 90% removal of TDS in the RO. If it comes in at 40, replace filters at 4. A hard and fast number isn't helpful without relation to the influent conditions.

Also, if you have TDS 0 water in a bucket for three weeks, why throw it out? You are adding nothing harmful, and if bacteria were to get into the bucket, what would it grow on? There is no food or nutrients in the water, therefore it would not reproduce. The water should be fine for quite a while. The only thing I would worry about it the water absorbing nasties from the atmosphere, and a good cover takes care of that.

[Melissa]

I'm looking forward to the day when I have to get a fresh bucket of water out because one or both of my dogs decide it looks pretty tasty and dunk their big heads in it for a drink. After the 2nd Monthly Elbow Incident, I'm not interested in carrying any more water downstairs than I have to. Since my dogs normally drink water out of 5gal buckets, this scenario is pretty likely. It's just a matter of time. That being said, I wonder what the TDS reading of RODI water + dog drool would be.

[georgiajams]

Also, if you have TDS 0 water in a bucket for three weeks, why throw it out?

I was wondering the same thing. I save my water for several weeks at a time in my brute trash cans (with lids) or in those 5g jugs. They aren't going to get anything in them during that time that the water wouldn't have been exposed to if it was sitting in my tank.

[goodfortune]

I was wondering about the phosphates, as I've heard that RO doesn't pick up phosphates (or silicates for that matter) as well as other molecules/ions present in the water. I'll ask the Kent Rep about phosphates/silicates and RO removal, and post some answers when I hear back from him. Wish I thought to ask last night .


- Michael

[Brian01]

Something to think about with DI water too, the ones that use color changing resins (in particular) add complex organic molecules to the water. I've never bothered to follow up exactly what they all are, but the colored dyes are at least part of it. This seems to have no detectable effect on most things, but it makes these waters almost useless for embryological work. The newer resins are supposedly better, but I still know many people working on development that avoid DI water, simply because it kills their embryos.

However, I still use the tap water purifier, and the water it produces is as good, except for that issue above, as our 300lb scientific grade ultrapure stupidly expensive deionizer in the lab. Just far lower capacity of course. I get 17-18 megaohm water (anyone know the formula to convert that to TDS), even after recharging the resins (I'm cheap). I also have a large carbon filter in line before it.

What ion exchangers do not get so well, and why the carbon is absolutely necessary, is non-polar organics (oils for example). They require either a charge or strong polar site to displace the ions on the column. I have no idea how well RO units do on these. Somewhere I have a table of data on this from our millipore rep (the guys who make our lab column) if anyone is interested, I'll try to track it down.

[Stanfill Reef]

Non-polar organics should easily be removed by the RO, but oils will tend to foul. You definetely want the GAC in front of your RO.