Hypo QTs and pH

[weez1959]

This is one topic that really intrigues me:

Whenever I have a QT set up I have all the trouble in the world keeping the pH in the right range especially when the salt is 1.009.
The reason for this post is I would really like a well explained (please ) technique on how to keep my pH in the right range, for instance I know that I shouldn’t raise the pH more than 0.1 a day but when I do an hour later it’s back to where I started , right now it’s at 7.8 which is pretty low. Sometimes I find it at 7.7!

So am I supposed to:

1) Keep adding buffer (Seachem is what I use) every couple of hours? If I do this I think the fish wouldn't be able to swim in the "thick with buffer" water And if this is the right way, it would probably be back where I started by morning!

2) Add something different that I don’t know about that would keep it more stable.

3) Add Seachem builder with the buffer?

4) Would Kalk work better or is this strictly for a reef tank?

Right now I’m doing 2 of 8 gallon water changes twice a day and adjust the new water with buffer but like I said it doesn’t last enough time to be able to make the next adjustment…

I’ll start with this and work from there….

[leebca]

The pH control of a hypo saline solution is a big challenge. Although hyposalinity is used to treat one particular disease: Marine Ich (Cryptocaryon irritans), it isn't as easy as one would like to think. Less stressful for the fish; more stressful on the aquarist.

When sea water is thinned, so are all the buffering agents. The ability for the water to hold its normal pH is compromised so something must help compensate for this. Adding more buffer to water that is too thin for the buffer to hold the pH, I think, is clearly not the way forward. Certainly adding alkalinity to the water defeats the purpose of the hyposaline solution, right? I mean, if the aquarist wants the buffers and alkalinity, then why thin them and add them back?

The answer is to force the water to change the pH and then to hold it there manually. Not easy but these are options:
1) starting with the proper pH, drip an alkaline solution into the QT to compensate for evaporation AND hold the pH;
2) make alkaline additions routinely.

The alkaline to use is probably not the pH adjusters, buffers, and alkalinity boosters (Kalkwasser), but of a solution of high pH water. The most potent alkaline solution available to the home user that doesn't adversely affect the fish is sodium carbonate (not sodium bicarbonate).

Try sodium bicarbonate first and if that doesn't give the best control by drip adding it, then move on to sodium carbonate. Sodium carbonate is made from sodium bicarbonate by baking sodium bicarbonate in the oven. Sodium carbonate added to distilled or RO/DI water is about as high a pH solution as the average aquarist will be able to attain. Dripped into the QT to compensate for water evaporation, the aquarist should be able to determine the concentration and drip rate to hold the pH in check.

In harmony with the above, all causes of lowering the pH must be addressed. One example of this is wastes. Wastes in the QT water cause pH to go down. All uneaten foods and fish wastes need to be removed from the QT in a timely manner.

Another example is the air around the QT. The QT must be in a location where the QT water can exchange gases with the air that is low in carbon dioxide. Putting the QT in a closed room where people have taken up much of the oxygen and loaded the air with carbon dioxide, drives the pH of the QT water down. There are more reasons that cause a drop in pH and many are covered here: Low pH: Causes and Cures by Randy Holmes-Farley - Reefkeeping.com. This article is technical enough (too much?) but can be read for just the advice and general information.

One of my disciplines is chemistry. I have access to chemicals most don't. The alkaline solution I make up is sodium hydroxide and drip a dilute solution of that in very carefully. No matter what alkaline solution is used, experience will lead to the right concentration and drip rates. Such a setup definitively controls and maintains the proper pH in a hyposaline solution.

[weez1959]

So what I should be doing is making up a batch of the alk solution from Mr. Farley's 2 part recipe and mix a small ammount into a 2l. bottle of RO/DI water and drip this into the QT at the rate of evaporation? Is this right or am I missing something?

[leebca]

It has been a while since I've reviewed Randy's two-part additive. If I am correct, then he is using a calcium carbonate system. What I'm suggesting you use to control pH is a sodium carbonate solution. The goal is to control pH, not add calcium nor alkalinity.

[weez1959]

One of the parts in his recipe has baked Sodium Bicarbonate which is what you were refering to in the post above. What I did this afternoon is bake 150 grams of Baking Soda in a 300 f oven for one hour and then mixed it into 1 quart of water.

I added 1 tsp. of this solution to a cup of fresh RO/DI water and slowly added it to the tank and the pH went up a bit and is holding better than the buffer but it still drops a bit. Is it OK to add this several times a day to keep it where it should be?

[weez1959]

I thought I would add a link to the recipe:
Chemistry and the Aquarium

[leebca]

Now I remember. . .

Use as much as needed to hold the pH in the 'right zone.' Ideally you'll get to the point where you'll know how much is needed to:
1) hold the pH;
2) keep the salinity near constant; and
3) hold the volume of the QT water near constant.

I think you'll find this method one of the least expensive and offers better control.

[weez1959]

Thanks Lee!
Yes, very inexpensive, I'm still trying to find a local supplier for Dowflakes for my DT. Using those Seachem products is rough on the budget
So far this morning the pH dropped a bit but not enough to go crazy. I'll bring it up to 8.3 in the next couple of days and I think finally I'll be able to keep it there.