Do It Yourself Blackwater Extract.

It's possible we've gone as far with this topic as we can.

The KH in my tank is 2, just edging toward 3. I would say this is low KH by anyone's standard. Not the lowest, but low.
Out of the tap KH is 4; I'll say 4, but it could have been somewhat less. You know how it is with test kits and colors.

Water hardness definitely plays a role, but my water has always been on the soft side, measuring about 4 with the test kit. Unfortunately, I couldn't get a reading at all with the kit I have, it's too old I guess. I'm getting a new test kit today and will see what's what with GH.

So ...
You can see my dilemma: obviously some buffering is lost in the tank, which would indicate the water is still on the soft side, and with a low KH to start with the pH should be dropping. I do not do frequent water changes, and I have lots of plant life, including plants that are naturally decomposing.

All the pieces are in place for a low pH but the pH is 7.2, regardless.
I'd like to know why, but I think we've exhausted all the possible reasons.
( -> I realize if I want a lower pH I need to add something, but I've decided to keep the pH as is.)

I appreciate the input on this thread and basically agree with what's been said. One thing I'd like to comment on:

I think a heavy bioload of fish will definitely contribute to the available organics in the tank, creating acidic conditions, and thereby affecting pH. As well, the decomposing organic material starves oxygen from the tank, which raises available CO2 and lowers the pH somewhat.

I've decided to add the oak leaf extract to my Dekeyseria tank. That is a true backwater fish that needs conditions similar to Discus.

The tank that's the subject of this thread (20 gallon Amazon) is in the process of being converted to a wild-type guppy tank (20 gallon stream pool) and many changes have been made already, so I'll not worry about pH and just go with the 7.2 as is.


This is how it looks today. That big floater is hornwort, for the babies.
The whole top used to be covered in water lettuce (Pistia stratiotes) which is a high maintenance plant that needs frequent pruning of old and dead leaves. It has gorgeous roots.

 

Oak leaves will definitely add that extra something to your Amazon tank.
Gather clean dry leaves just the way I described above for making extract. Instead of making the extract, though, soak the leaves for a couple of hours until they sink on their own. Push them down in the water to get things started. If you boil them for a few minutes they will sink quickly.

In my area of collection photo you can see the leaves are well submersed in the water due to waterlogging.

The leaves will break down in the aquarium over time, maybe two years, so you will have to replace them. You can store replacement leaves indoors in a dry place.

In a 55 gallon, I'd start with about 10 leaves in a loose pile over to one side of the tank. Observe which fish tend to favor that area.

 

Hi! I need to clarify something I wrote. I said oak leaves would break down in the aquarium over time, about two years. That's wrong. I was thinking of wood when I wrote that. Wood takes about two years or longer, depending on how soft it is.

Oak leaves break down kind of fast. You need to replace them every few months, but it varies. Other leaves such as leaves from rubber plants take longer to break down. There you're talking about a year or longer. Tough thick leaves take longer to break down than thin crispy leaves.

Collected wood takes about two years to break down. Soft woods take about two years, and hard woods take longer. The best thing to do is to keep an eye on the decor and take out anything that is breaking down faster than you would like it to. Keep some extra clean dry leaves and some pre-boiled wood handy.