Driftwood = pH swing?

[Kalavek]

I've been caught off-guard again. Thanks to everyone who recommends putting anything new in quarantine, no damage has been done. Yet.

I keep reading that plecos like driftwood, so I stopped by PetSmart the other day and bought a medium piece off their shelves. The brand on the front is "GEOsystem", though on the backside of the label (and not visible without removing the wrapper) is a Hagen logo. A second sticker says that this is a piece of Malaysian Wood.

The backside of the label also states: "Natural Aquascape wood is a natural product that has been cleaned to remove extraneous material and to ensure its safety in aquariums." It goes on to mention that it will release some tannin, and that it won't harm your fish because it's actually good, but the color can be removed using carbon.

I hit up Google - read about tannins, driftwood, boiling, bleaching, baking, parasites, not using ocean wood in freshwater aquariums - and how some people are highly paranoid of contamination while others will simply drop a store-bought log right into the tank.

My 5g quarantine tank was already filled with Primed water just to see what this log will do to the environment. No gravel, no carbon, no beneficial bacteria. The water's pH was at 6.8, temperature around 77 degrees, and everything came back negative on my API Master Test kit. The only filter in the HOB is the floss screen to catch particulates. A submersible water pump is suctioned to one wall inside to keep the water moving.

I tossed it in last night, gave it a good brushing to get any dust and crap off, and it's been in there for a bit more than 24 hours now. The water has a very slight yellow tinge to it now, less than I expected - and a lot of the finer particulate is coating the tank's walls. I tested the pH when I came home tonight to discover it has completely crashed - it reads 6.0 on my API chart. It could actually be a lot lower, since that's just the lowest value the test will read.

Now I'm not all that shocked that something I didn't expect happened - but can someone explain it to me?

[Dino]

Any idea what your hardness is?
With a low hardness, you will have very little buffering capacity.
So, what little organic acids came off the wood, caused your water's pH to drop.

[Kalavek]

I think you're right. We seem to have very soft water here according to my test-strips.

Took a quick look around for info on adjusting the alkalinity, but I'm wondering if that's the right way to go about things. If I start doing water changes on the quarantine tank, will the wood begin having less impact on the pH?

[punkrockfish]

fish are pretty good at adjusting to pH, and messing with it can cause a lot of problems. i wouldn't worry about it too much, but yes, frequent water changes will keep your pH higher.

[misterking]

It shouldn't only take 24 hours for there to be a visible change in the water colour and pH, driftwood that's been treated properly but the company (or as it suggests on the label you quoted) should take at least a week to change the water quality. I would suggest taking it out and soaking it for a day or so in a bucket or something, if this is an undesirable change. But as punkrockfish said, fish are quite goof at adapting to pH, and pH6 isn't all too low, your pleco and zebra danios should cope fine with it.

[Kalavek]

Thanks guys.

As I mentioned, I did not put the log in my populated tank - it's still in my 5g quarantine tank. If I had put it in the larger tank I probably would not have seen the pH change that fast. The color change I saw in the water was slight, but even after a day I could see it.

I've been experimenting with it a little - I have been changing out all the water in the 5g daily, and dosing the new water with Prime (because I don't know if chlorine/chloramine will accumulate in wood). I've been using the heater, but that's mostly because it's a new heater and I'm trying to get it set to the same temperature as my main tank. I've also still got the submersible pump and my HOB running just to catch any crap floating around.

After the water circulates for a day I tweak the heater, check the pH, and change the water. The wood is still tossing the pH down, but I've already noticed it's changing slightly less with each water change.

At this rate it could take up to a couple weeks to get it to a pH of 6.8, but I'm not going to do this for that long. I'm doing a water change on my populated tank tomorrow, so I'll put the tank water on the log and see what happens. After that I'll probably drop it in with the fish.

[Kalavek]

Quick update on these driftwood tests.

I drained the qt tank and put in my used tank water, pH was at about 7.2. After about a day the log pulled the pH down to about 6.8 - which isn't too bad considering that matches my tap water.

The log is in my populated tank finally - between that and the 5-gallon water change, the pH is currently sitting at about 6.8.

My plec didn't hesitate much - shortly after I stopped messing with the decorations he started checking it out.