Do It Yourself Blackwater Extract.

The pH in my Amazon tank used to run very low without any help from me. It would consistently read yellow with a test kit. That's 6.0. Sometimes after a healthy water change it would read at 6.4, and then gradually slip down towards the 6.0 again.

Lately, though, my pH reads the same as the tap water which is 7.6.
I don't get why, because I don't think I'm doing anything different, but there it is.

So I'm trying something that European hobbyists always talk about, which is add an extract of something to the water. I belong to a Corydoras catfish club and may of the members are from Northern Europe. A member from Norway tells me that she uses oak bark extract in her tank, which she buys from a German supplier.

I modified this idea a little and came up with oak leaves. Oak leaves are very popular for creating the leaf litter that so many catfish (and other fish) like, so I figured it would work.

Here's how I made about a liter of oak leaf extract:

1. Collect some oak leaves.
They must be clean and dry before you use them, but they can be wet when you collect them.


The collection area is important. It needs to be in a place where the leaves are not exposed to pesticides, road tar, or other pollutants. This culvert and stream bed is in Henrico County, Virginia. I've collected lizard's tail (Saururus cernuus) for use in the aquarium from here before, so I know this area is okay.

2. Choose about 15 to 20 large, intact leaves. They should be dry and clean. Wipe off any insect debris, cocoons, dry dirt.


These leaves dried in the sun. I think they are really pretty.

3. Soak the leaves in about one and a half liters of water in a pot which can later be boiled.
If you have an old pot, fine, but this procedure will not harm your regular cooking pots.

I left my leaves to soak for 48 hours, but 24 would probably work, too. Let's say somewheres between 24 to 48 hours of soaking in plain, cold tap water.

4. Boil the leaves in the same soaking water for about 15 minutes.
Longer will not produce a darker brew, so I'd say 15 to 20 minutes is plenty.


Here is what my "witches' cauldron" looks like after the boiling is over. The extract looks and smells like a dark brewed black tea. The reddish color reminds me of Yorkshire Gold Tea, from Yorkshire England. My favorite.
Was I tempted to sip a teaspoonfull? Yes, but I didn't.

Let the liquid cool.

5. Filter the cooled extract through a paper filter.
I set up the bottle I was going to use with a funnel fitted with a paper coffee filter.
You have to pour the liquid slowly, and change the filters when the trickle slows to a slow drip.


I went through three paper filters to get a liter+1 cup of extract.

I'm doing some experiments with a cup of plain water to find out how much extract it takes to lower the pH in a significant way.

So far it looks like 2 teaspoons of extract in one cup of water will lower the pH from 7.6 to 7.2. A lot of time has elapsed to get this far, because I add the extract 1/2 teaspoon at a time. The water+extract sits several hours between readings to see if the pH will lower itself further.

I consider a valid reading to be the same reading, obtained three times in a row, over a period of 36 hours.

If anyone knows how to make a stronger concentration, please post your ideas here!

 

I know about peat, but it's not the same thing as tannin staining from leaves and bark. I think they each bring their own character to the water and they each have something different to add.

Lemon, do you use peat yourself? In which tank?
Is it the same kind as what we would put around outside plants?

James, I have snails in the tank mentioned above. I've tried leaf litter before and it's awesome in a long sand tank with natural lighting.

 

Sorry - I didn't explain myself right.

What I mean is, I know peat stains the water and lowers pH.
I wanted to try something more like what would be the case in the natural habitat - water staining from leaves and bark in the water.

The Amazon river basin and its drainages are not peat bogs, as far as I know.
So, I wanted to stay away from peat this time, and see if I could accomplish the lower pH with the oak leaves.

I think it will take a lot of this extract to do that, from my "experiments" so far ...

BTW, I think your Discus tank looks great!

 

Pretty much all the catfish I own, have owned, and will own come from the Rio Orinoco basin, which is a blackwater system. I've never had to worry about lowering pH until now. Even so, the water in the tank in question is not clear. It's a pale brownish-yellow color, which sounds nasty but looks good.
My KH is low, the water is stained, I have tons of wood, plant leaves decay regularly but still the pH has gone up. It used to be quite low, as said above.
Do you have any ideas as to why the pH has gone up?

 

Lemon, I'll answer some of your questions.

Yes, the rocks were collected over the years from river and stream beds. I'm sure they are quartz based and inert. I use regular Estes' 3-5 mm aquarium gravel in this tank. No shells or coral. All of these rocks and gravel have been in the tank for years. The tank is 10 years old.

The last time I took a KH test was about 5 years ago.
At the time the KH from the tap was 4. (about 62 ppm.)
The KH in this tank was between 3 - 4. (between 50 - 62 ppm.)
(Using API test kit)
I figured the low-ish KH was the reason the pH consistently dropped. Since that was a desirable condition for me, I didn't worry about it.

I will do a new KH test over the next day or so. Do I need a new test kit?

The pH out of the tap is 7.6 or the darkest blue on the test card, using the API test kit. I suspect it's even higher than that, and the kit can't measure it. It's been this way for years and there seems to be no seasonal change.

I keep notes on my tanks, and this tank used to routinely read about 6.0 on the test card, and I think it was even lower, the color was such a bright yellow.

My wood is old. There are three large pieces and they have been in the tank for years, the oldest piece is over ten years old. Could it be that they have stopped leaching?

Also, the other thing I just thought of is that there are far fewer catfish in this tank, now, than there used to be. I decided a gravel tank is not good for most catfish and now I just keep a couple of small Chaetostoma in there.

I appreciate you sticking with me on this, and I'll take on board any ideas you may have.
I'm primarily concerned with why the pH has dropped, not how to lower it with extracts, because I think I already know how to do that.

Do you think the wood stopping leaching is a possibility? And fewer messy fish? All my fish are very small; I have lots of 3-5 mm ramshorn snails.

James, I will be at your house with some very large 5 gallon water bottles in about two hours! Is .10/gallon fair? [laughing] JK!