Question about RO water...

[Ron Sower]

I could probably look this up elsewhere on the internet (because you know, everything you read there is true!  ), but why not continue to tap the brains of the true sources of real honest knowledge here on Mugwump's Fish World...?

...I've used nothing but RO water in my community tank, yet around the edges of the top where the sponge filter sprays burst bubbles there is a build up of white evaporative salts of some kind...

...Does the RO process remove CaCO2...is that what this is?...it's easy to remove, but unsightly...

...I haven't added any liquid ferts for quite a while now...and there have been at least 4x 20% WCs since then..

[wallace]

The RO, if its working right, would remove almost all (95%+/-) of the CaCO3 and there shouldn't be deposits. I use RO also...

Do you have a TDS meter? They are like $14 and the TDS reading will tell you if the RO filter is working as it should. To some extent it depends on what minerals are in the source water, but the TDS of the RO should be around 1% to 3% the TDS of the source water.

Another thought.... your air is so dry, there would be much more evaporation than ordinary mortals experience in their tanks, and that would contribute by concentrating whatever minerals you start with.

[BillT]

Like Wallace said, the RO should remove all (or most) of the carbonates.

Some carbonates could be restored to the water by CO₂ dissolving in the water and then combining with water molecules (H₂O) to make H₂CO₃ at some low level. This could combine with other dissolved ions (if present) to make things like NaHCO₃ or KHCO₃ or others. I would guess this would be a small effect.

Another source of chemicals would be due to the food input. A lot of prepared foods contain a lot of phosphate (as well as other chemicals). This could also form a precipitate.

[Ron Sower]

The RO, if its working right, would remove almost all (95%+/-) of the CaCO3 and there shouldn't be deposits. I use RO also...

Do you have a TDS meter? They are like $14 and the TDS reading will tell you if the RO filter is working as it should. To some extent it depends on what minerals are in the source water, but the TDS of the RO should be around 1% to 3% the TDS of the source water.

Another thought.... your air is so dry, there would be much more evaporation than ordinary mortals experience in their tanks, and that would contribute by concentrating whatever minerals you start with.

Thanks, Dan...I don't have a TDS meter and should get one soon....you have confirmed what I thought about amounts of the CaCO3 (forgot in my original message that it wasn't CaCO2)...and absolutely right about the excessive evaporation.  Thanks again...

[Ron Sower]

Like Wallace said, the RO should remove all (or most) of the carbonates.

Some carbonates could be restored to the water by CO₂ dissolving in the water and then combining with water molecules (H₂O) to make H₂CO₃ at some low level. This could combine with other dissolved ions (if present) to make things like NaHCO₃ or KHCO₃ or others. I would guess this would be a small effect.

Another source of chemicals would be due to the food input. A lot of prepared foods contain a lot of phosphate (as well as other chemicals). This could also form a precipitate.

Ahhh...forgot about food!...Thanks, Bill...

[LizStreithorst]

I didn't know about phosphates in fish food.  No wonder the fish enjoy a good WC.

[waterboy]

Don't you re mineralize the RO water.  I heard you have to add some minerals back in to the RO water because the fish need some of the minerals that the RO process takes out.

[LizStreithorst]

That's the party line but I have my doubts as to it's validity.  I used 100% unreconstructed  RO for years.  I had no problems at all.  I came to the conclusion that fish, like us, get the minerals they need from the food they eat.

[wallace]

I agree with Liz, except that with fry there is a lot of anecdotal evidence that fry can have developmental problems in straight RO. It appears they need a little calcium in the water, but nobody knows how much. The thing is, not all RO is created equal - some people have TDS 0, some have TDS 15, and at 15 ppm there may be enough calcium.

[wallace]

The RO, if its working right, would remove almost all (95%+/-) of the CaCO3 and there shouldn't be deposits. I use RO also...

Do you have a TDS meter? They are like $14 and the TDS reading will tell you if the RO filter is working as it should. To some extent it depends on what minerals are in the source water, but the TDS of the RO should be around 1% to 3% the TDS of the source water.

Another thought.... your air is so dry, there would be much more evaporation than ordinary mortals experience in their tanks, and that would contribute by concentrating whatever minerals you start with.

Thanks, Dan...I don't have a TDS meter and should get one soon....you have confirmed what I thought about amounts of the CaCO3 (forgot in my original message that it wasn't CaCO2)...and absolutely right about the excessive evaporation.  Thanks again...

Ron, there are a few TDS meters that don't have temperature compensation and will give confusing comparisons when samples are at different temps. I like the HM Digital TDS-3, it has the compensation and costs about the same.

[Ron Sower]

The RO, if its working right, would remove almost all (95%+/-) of the CaCO3 and there shouldn't be deposits. I use RO also...

Do you have a TDS meter? They are like $14 and the TDS reading will tell you if the RO filter is working as it should. To some extent it depends on what minerals are in the source water, but the TDS of the RO should be around 1% to 3% the TDS of the source water.

Another thought.... your air is so dry, there would be much more evaporation than ordinary mortals experience in their tanks, and that would contribute by concentrating whatever minerals you start with.

Thanks, Dan...I don't have a TDS meter and should get one soon....you have confirmed what I thought about amounts of the CaCO3 (forgot in my original message that it wasn't CaCO2)...and absolutely right about the excessive evaporation.  Thanks again...

Ron, there are a few TDS meters that don't have temperature compensation and will give confusing comparisons when samples are at different temps. I like the HM Digital TDS-3, it has the compensation and costs about the same.

Thanks again, Dan...