Reverse osmosis water Q's

[heresmike]

Looking for information from someone who is experienced with using reverse osmosis water in their tanks.

Someone gave me a recommendation to use a ½ tap water, ½ ro water mix when doing my partial water changes. I did a google search, and on a couple websties I read that if you mix the tap and ro water to use in your partial water changes, you don’t have to add anything to the ro water to replace the necessary trace elements.

Does anyone here do this? If so, does it effectively lower the hardness and pH? Does it cause any instability?

Also, if you have a reverse osmosis filter system in your home, I’d be interested in hearing about your setup (gpd / storage tank size / placement … etc).

Thanks.

 

[waterwatereverywhere]

I've used an RO unit for a few years now. For most of that time it was on a reef tank, so there wasn't a problem with trace elements because it all came from the salt. But now I use it on my FW tank.

For FW, as you say RO water doesn't contain enough minerals for the fish and plants. But IMO mixing it with tap water defeats the object - yes you get the minerals back in for free instead of buying supplements, but you also get lots of the nasties the RO unit's taken out. For instance, my tap water tests at least 5ppm for phosphate - it's untraceable in my RO water. If I mixed it with tap water I'd be back to 2-3ppm. I use Kent RO-right to remineralise it, at least that way I know that only the "good" stuff is going back in.

I've had no instability so far, although the tank hasn't been set up for all that long. The general hardness and kH are zero from the RO unit and the pH is 7.0. Using the Kent stuff you can raise it to what you want; I want soft water, but there are directions for amounts to add from Discus tanks through to Lake Malawi. The pH has settled at around 7.2-7.3, I guess this is partly because of the RO-right and partly because of the oxygenation of the water - you need to aereate RO water before adding it to the tank because it's deoxygenated.

I'm not sure what make my unit is, what an admission that is! - I bought it as recommended from a very good marine lfs. Gallons per day depend on the weather! - it does less on a cold day. When I was filling the tank up from scratch it was on constantly and I was getting about 13 a day from it, but it does it much quicker in the summer.

We have a joint garage/utility room, which already housed the washing machine. The RO unit is fed by tapping into the cold water pipe leading to the washer. From the unit it goes to a 2-gallon reservoir - when that's full it cuts off. A pipe from the reservoir goes to a tap on the garage windowsill. (We use it for all our drinking water as well.) I've got a valve in that pipe so I can divert it all into a bucket when I want a bucketful. I've put the pipe which takes the discarded water away into the washer's drain pipe.

HTH

 

[heresmike]

But IMO mixing it with tap water defeats the object

I guess my thinking was that by mixing it with tap water, it would lower the phosphate levels and pH levels, etc, to an acceptable level, and solve a couple other things I see as problems ... ie, producing/storing enough to do my water changes, getting the water to the right temp. Do you heat the water in a kettle or something?

From the unit it goes to a 2-gallon reservoir - when that's full it cuts off

So, do you store the ro water elsewhere so you have enough when it comes time to the your water changes? If so, in what type of container?

you need to aereate RO water before adding it to the tank because it's deoxygenated

How do you go about doing that? If I were to mix it with tap water, would I have to aereate it?

Thanks again.

 

[waterwatereverywhere]

Yes, it would lower your phosphate levels, etc - I suppose it's down to preference and how delicate the fish are that you want to keep. But I don't have a problem with producing enough for water changes. I do 5 gallons at a time. When I want to do a change, I open the valve on the pipe leading to the tap and divert it into a 5 gallon bucket. That way it empties the reservoir first and then because the pipe's open it carries on making fresh water, so carries on dripping into the bucket. When the bucket's full I put a spare heater and airstone in for 24 hours before doing the water change. If you were to mix it with tap water then I would think there's less need for aereation. But I really don't have any problems with not using tap water, and I think there are benefits.