Would switching to RODI water cause my carbonate hardness to drop?

[Juju2773]

For about a month now i switched to RODI water for my 75 gallon tank. I do a weekly 10 gallon waterchange. I use a simple test strip each week just to keep an eye on things. I have noticed my KH/ carbonate hardness is steady going lower. Its at 40ppm today. Also, my General hardness was going down as well, but it has been fixed.
Should i be concerned? The only other things ive been doing is I manually dose a few drops of magnesium and kalkwasser about 3 times a day(to fix the GH, and it has worked). My GH is back up to 180ppm and staying. Not sure about KH/alkalinity or what i should do. I did not expect this with RODI water. I bought the 5 stage system BRS. The TDS meter says 0 on the filtered water.
I use the Red Sea salt mix in the blue bucket. I did not have any issues before i switched to RODI.

 

[spsick]

It could if you were using tap water before but more likely it’s coral or coralline algae consuming it.

 

[Juju2773]

I was using distilled water before. My levels pretty much stayed the same. I do have a good amount of coraline, but i did before too so im not sure its that. I have had a large amount of brown hair algae start up after the switch as well, but i think that is going away slowly. My nitrates and phosphates are ok.

 

[Jekyl]

I wouldn't put my faith in any test strips. My first step would be to get a better test kit and a second opinion from your LFS.

 

[Juju2773]

I do have good calcium, phosphate, and hanna salinity tests so far. They are expensive so i pick one up every once in awhile to add to my set. I just use the strips often if theres not really any problem for monitoring.

 

[Randy Holmes-Farley]

40 ppm carbonate hardness is almost certainly way off base. It corresponds to 2.2 dKH, which just does not happen in a reef tank.

I’d get a real alkalinity kit.

Distilled and ro/di (assuming it is functioning) are both fine and contain no alkalinity.

 

[Randy Holmes-Farley]

Don’t bother measuring GH. It’s not a useful measure in seawater , being a weird combination of calcium and magnesium that you cannot disentangle.

 

[Juju2773]

40 ppm carbonate hardness is almost certainly way off base. It corresponds to 2.2 dKH, which just does not happen in a reef tank.

I’d get a real alkalinity kit.

Distilled and ro/di (assuming it is functioning) are both fine and contain no alkalinity.

Thanks. I guess ive got to get a new test kit. But what can i do to raise the carbonate hardness?

 

[PeterEde]

I do have good calcium, phosphate, and hanna salinity tests so far. They are expensive so i pick one up every once in awhile to add to my set. I just use the strips often if theres not really any problem for

As soon as you suspect a problem use the more accurate hanna checkers.

 

[Juju2773]

40 ppm carbonate hardness is almost certainly way off base. It corresponds to 2.2 dKH, which just does not happen in a reef tank.

I’d get a real alkalinity kit.

Distilled and ro/di (assuming it is functioning) are both fine and contain no alkalinity.

Well the RO unit is brand new and the TDS meter testing the water as it exits the final filter says zero so im sure its working fine. I am just very confused because my levels have been always pretty good and very stable until now.
I thought about it... and i Did use my wood burning stove this weekend. Its Massachusetts and getting colder here. So...Possibly that made an issue? I am fairly new still to reefing and learning my way. I only have a few softies, mushrooms, an anenome, and fish right now. But i really would love some montipora cap. I was hoping to finally be able to try a couple sps with a real RODI water unit.

 

[Randy Holmes-Farley]

Thanks. I guess ive got to get a new test kit. But what can i do to raise the carbonate hardness?

Absolutely nothing unless and until you know you need it. Right now you have no such knowledge.