Need help with low pH in a 225g

[jabel]

I've been stuggling for the last few months trying to keep my system pH above 7.8. Each time it goes below the tips on several of my sps burn. The rest don't seem to grow much. I've read just about every article available and talked to many friends with well behaved tanks and I just can't figure out how to fix this. My pH ranges from 7.8 to about 8.1 during 24 hrs. My alk ranges between 9 and 11, my ca is around 400 and my mg is 1350. I've tested these continuously over the last few months. Here's my set up. I use a small GEO ca reactor with a 2nd chamber and depending on what I'm doing, it seems to be able to maintain my alk. I run calk in my top off and I have that scheduled to run during my low pH period. I use three 400w MH lights that run about 8 hrs each from 4pm till 1am. I have a refugium that runs a small home depot light on an opposite time to the tank and a small frag section in my sump with a 250w MH that runs from about 3am till 10am. My low pH comes between 10 am and 4pm. I also run a bubble master 250 skimmer.
I've replace my pH probe and double checked it with a 3rd meter. I tried agitating the water surface as much as possible to get better co2 exchange and my ca reactor efluent exits near my skimmer intake. I usually leave my windows open each night so my house should have a good air exchange with the outside as well.
Any thoughts? I'm out of ideas and getting more and more frustrated.

Thanks,
Jeff

 

[David MC Lee]

Kalk does a good job of keeping my 800G tank at 8.2 ph. I use Mrs. Wages® Pickling Lime for the job. I get it at stores that sell canning supplies.

 

[mpoletti]

My pH ranges from 7.8 to about 8.1 during 24 hrs. My alk ranges between 9 and 11, my ca is around 400 and

Can you detail this a little more? A 2 dkh swing in 24 hours may be leading to more coral stress than the lower PH. Is your low PH when your lights are off? Do you run a refugium on reverse lighting?

 

[jabel]

David, yes I use Mrs Wages for adding kalk to my top off

Mark - yes, my pH swing from 8.1 to 7.8 during 24 hrs. The low is when the main tank lights and the frag light are off, around 1pm. I do run my fudge on reverse lighting cycle to my tank. I also have a frag section in my sump that runs opposite the main tank lighting but only for 8 hrs or so. My alk is actually stable at 9 dkh right now. The range I gave for alk was just over the last 3 months and is due to my tweaking the system while trying to figure it out.

Also, my CO2 for the reactor shuts off when my pH goes below 7.93.

Finally, I removed some tank water and equilibrated it outside for 60 min and at the time it measure only 0.05 pH units higher than my tank.

Anything else that I can provide details on?
Thanks,
Jeff

 

[mbaychuk]

I had noticed my ph was dipping also below 7.8 at times so what I first tried was shutting off my co2 to my geo rx for 1 or 2 days jusy to see if I would still get the ph swings. When I tried this the ph would not go below 8.0 not matter what time of the day. So what I did was slow my co2 injection into the rx and shortened the time period that the co2 is on. I have the co2 solenoid off during the night. I have a 430g system with a large geo rx and I also use reverse lighting on the refugium.

 

[jabel]

Still having problems. Anyone with some advice? This morning my tank pH was at 7.82 when its usually above 7.9, so I'm sure my tank pH will go below 7.8 today. This means more dead coral.

I think I'm ready to give up.

 

[David MC Lee]

I would shut off the CA reactor, make sure the CO2 is turned off. I've seen a lot of valves leak. What is the ph of your make up water. Your Kalk should be I think around ph of 12.

 

[jabel]

No leak in the CO2 valve, but I'll try anything at this point. What should I expect when I shut off the reactor? Yes, my kalk is above 11. But since the days are cooler the evap isn't as much and amount of kalk added is less which might explain the lower pH, at least today.
Thoughts??
Thanks,
Jeff