pH in QT

renisel · #1 11/14/2007, 05:20 PM

I've had a 20 gallon hyposalinity QT set up for about a week now and I'm having an impossible time keeping the pH anywhere near where it should be (according to my test kit, it's been between 7.4 and 7.8 most of the time). The alk is at about 2.2 meq/L and I have a pretty large air pump providing aeration. I'm thinking I should try adding some kalk, but I'm not sure what a safe rate would be. Any input would be appreciated. Thanks.

bertoni · #2 11/14/2007, 06:24 PM

What kit is being used, and is it rated for fresh water? I've forgotten how flexible test kits are in that respect. What animals, if any, are in the tank?

renisel · #3 11/14/2007, 06:41 PM

The pH test is an Aquarium Pharmaceuticals test for saltwater. I tested the 1.009 SG water right before putting it in (after mixing it in another room) and the pH was about 8.4--so I think it's an actual pH drop due to higher CO2 in that room, and not just a testing issue. An hour or so ago, I took a cup of water out of the DT, which has a pH of about 8.4, and set it next to the QT. In a little while I'm going to check the pH of that to see if it has dropped as a result of being in the other room (further evidence as to whether it really is due to higher CO2 in the room). The tank has two small green chromises and two small maroon clowns (small = ~1").

bertoni · #4 11/14/2007, 07:43 PM

That sounds like a good experiment to do. You'd need to aerate the cup of water to measure the pH effect. An airstone would. I'd also add a powerhead. They provide a large amount of aeration, too, and can help with surface slime.

Fish should be able to tolerate rather low pH fairly well. Corals have more trouble with that.

renisel · #5 11/15/2007, 12:43 AM

The pH didn't drop in the water from my DT that was placed in the room with the QT; but the pH went up in a cup of water from the QT with an airstone in it in the same room. So apparently it was an aeration/circulation issue. I've had a 170 gph powerhead and two airstones attached to a pump rated for a 100 gallon tank running in my QT for about 3 hours now with no noticeable pH change. Will it take a long time for the pH to rise, or do I still need to do more to increase the aeration?

tmz · #6 11/15/2007, 02:39 AM

I'm lost on this one. Wouldn't the ph be expected to be low with hyposalinity? As long as it doesn't move around alot I don't think it will hurt the fish.

renisel · #7 11/15/2007, 02:57 AM

Quote:

Originally posted by tmz
I'm lost on this one. Wouldn't the ph be expected to be low with hyposalinity? As long as it doesn't move around alot I don't think it will hurt the fish.

If you just add salt mix and no additional buffer or base, the pH will probably end up on the low. But you still want to get the pH up to where it normally is. Low pH in hyposalinity will have the same negative effects that it would in at normal salinity.

tmz · #8 11/15/2007, 03:12 AM

Quote:

Originally posted by renisel
If you just add salt mix and no additional buffer or base, the pH will probably end up on the low. But you still want to get the pH up to where it normally is. Low pH in hyposalinity will have the same negative effects that it would in at normal salinity.

And what are those negative effects in a fish only quarantine tank?

bertoni · #9 11/15/2007, 03:36 AM

The airstones probably aren't as effective as another powerhead would be, but aerating the tank could take a few hours in any case.

renisel · #10 11/15/2007, 12:15 PM

Quote:

Originally posted by tmz
And what are those negative effects in a fish only quarantine tank?

I'm not exactly sure. I've just been told that it causes more "stress". I never looked into it that thoroughly because it seemed pretty reasonable. Significant variations in pH will have large effects on many physiological systems. If nothing else, there is a decent amount of contact between the fish's inner workings and its external environment at the gills. So I could see where higher pH in the water might raise the pH of the blood, forcing the kidneys to work overtime, and possibly altering a number of other internal processes. Maybe you're right and it doesn't really make a difference; but I'd prefer to be on the cautious side, especially when the fish are already in less-than-perfect health.

tmz · #11 11/15/2007, 01:40 PM

Hi renisel, I don't have a position on this. I'm trying to learn more about hyposalinity in qt both as an active treatment and a prophylactic treatment. I have managed qt with regular sg for years and relied on copper for treatment if symptoms appear. There are many mixed opinions such as Tangs fare poorly with copper etc. Not my experience. Or, Tangs can get kidney damage from hypo,etc. I like being cautious and manageing stress. Have you considered that you are more likely to get ph variation if dosing buffers and that the variation might be more harmful than a consistent low ph?

renisel · #12 11/15/2007, 04:37 PM

Quote:

Originally posted by tmz
Hi renisel, I don't have a position on this. I'm trying to learn more about hyposalinity in qt both as an active treatment and a prophylactic treatment. I have managed qt with regular sg for years and relied on copper for treatment if symptoms appear. There are many mixed opinions such as Tangs fare poorly with copper etc. Not my experience. Or, Tangs can get kidney damage from hypo,etc. I like being cautious and manageing stress. Have you considered that you are more likely to get ph variation if dosing buffers and that the variation might be more harmful than a consistent low ph?

The purpose of the buffer isn't so much to raise pH as to hold it in the desired range and prevent drastic swings. So, regardless of where you have the pH, I think keeping alkalinity up is a good idea. As for dosing kalk to raise the pH, yes, I had considered the potential negative effects of rapid pH swings. My main intent in posting the original question was to find out what a safe rate would be for adding kalk (which would correlate to a safe rate of change in pH). As it turned out, I didn't need kalk so much as additional aeration. I was concerned that suddenly flipping on a powerhead that would give me more than 8x turnover per hour might rapidly increase the pH too--but, if anything, the pH increase is coming along more slowly than I'd hoped.

tmz · #13 11/15/2007, 05:48 PM

As for limewater. There is a section in "The Reef Aquarium III",Sprung and Delbeek, wherein they give the amount you can dose within a one hour of time without spiking ph.For me it works out to 1 gallon of saturated(2 tsps per Gal)limewater per hour on a 400g system. So you could safely dose 5% of that on your 20g per hour 3 or 4x a day or in a four or five hour nightime drip.

bertoni · #14 11/15/2007, 07:39 PM

The pH of the hyposalinity tank should be reasonably close to that of full-strength saltwater if the aeration is good enough. I'd have to know more chemistry and be able to compute the solubility of carbon dioxide at the various salinity levels to be more specific.

What is the pH now?

renisel · #15 11/15/2007, 08:32 PM

The pH is still no more than 7.8, and I added another powerhead that's supposed to give 125 gph this morning. I'd think that the 300 gph from the powerheads plus the 125 gph from the power filter would be providing enough circulation to boost the pH more than that. I'm thinking about adding a third powerhead, but I can't find the cover for its intake.

bertoni · #16 11/15/2007, 08:40 PM

I think that 7.8 is acceptable, even for corals. The circulation is probably good enough. Adding some buffer should give it a small tweak upward, if you're worried. You might try aeration a cup of of water outside for a few hours. That'd tell us whether the indoor carbon dioxide level is an issue.

rickyb · #17 12/24/2007, 01:31 PM

Ahren, is the QT lit up? If not, put in a light over it and see if the PH rises. Also give me a call and read your PM's as they are getting old as 11/21