Bogwood = Higher pH

[njparton]

I live in a soft water area and hence the pH in my tank has always been lower than that of my tapwater (which has a pH of 7) at around 6 to 6.5. I think this is down to 2 reasons:

1. low buffering capacity of the water; and/or
2. a piece of slate with a brown (iron?) band/vein about 1mm across and a total of ~40cm in length

Yesterday I bought some bogwood and soaked it for 24 hours in some warm dechlorinated water.

I put it in my tank about 4 hours ago as replacement for the slate and as I predicted/wanted, the tanins in the bogwood are making the water go brown (which I like and think is more natural looking).

I wanted to make sure the pH didn't drop too far as I'd read in this forum and elsewhere that the tanins will reduce pH. But I've just measured the pH and it's between 7 and 7.5!

Have I got my facts wrong about the tanins or did the metallic vein in the slate really have that much effect on the pH?

Should I expect the pH to drop again?

 

[Alien Anna]

Sometimes doing a large water change can temporarily increase pH (for some technical, chemistry reasons I'm not sure about). Keep an eye on it but the bogwood should start to subtly lower your pH over the next couple of months.

 

[njparton]

Sometimes doing a large water change can temporarily increase pH (for some technical, chemistry reasons I'm not sure about). Keep an eye on it but the bogwood should start to subtly lower your pH over the next couple of months.

A couple of hours after changing 25% of my water an it's usually down to at least 6.5.

I think that slate was a bad idea....

Love the bogwood (so far...)

 

[Lateral Line]

Slate is a metamorphic rock, generally quite inert in a tank. This vein, is it just a colour variation or crystalline? If crystalline, it is possible the slate fractured at some time and the crack was filled with calcite from percolating water, in which case it would fizz with vinegar, although in the high pressure regime where slate forms, it is more likely to fill with quartz which is also inert.

 

[njparton]

Slate is a metamorphic rock, generally quite inert in a tank. This vein, is it just a colour variation or crystalline? If crystalline, it is possible the slate fractured at some time and the crack was filled with calcite from percolating water, in which case it would fizz with vinegar, although in the high pressure regime where slate forms, it is more likely to fill with quartz which is also inert.

It's not crystaline, I'm judging it to be either iron or mudstone (my geology isn't that strong) although I'm thinking mudstone would be quite weak in comparison and I should therefore be able to seperate the slate into two pieces?

I certainly think it's iron now. Just measured the pH again and it's still 7+. I thought tanins would have an immediate impact?

The only hypothesis left is that the iron vein really did impact on pH quite heavily and that tanins are likely to reduce pH, just not as quickly?

I think most of my fish and plants are suited to a lower pH as most are Amazonian in origin (apart from from the clowns maybe!)

 

[njparton]

Hmm, in fact my water seems to be getting even more alkaline... over 7.5 now...

Any ideas?

 

[Lateral Line]

Iron wouldn't raise your pH, in fact, your plants require a source of Iron, that is why a lot of plant keepers put some laterite in their substrate. The rock is no longer in your aquarium?

 

[Alien Anna]

Hmm, in fact my water seems to be getting even more alkaline... over 7.5 now...

Any ideas?

Then you have some carbonate in there, somewhere. What sort of gravel or sand do you have?

 

[njparton]

Iron wouldn't raise your pH, in fact, your plants require a source of Iron, that is why a lot of plant keepers put some laterite in their substrate. The rock is no longer in your aquarium?

No, I took it out. I was thinking the iron LOWERED my pH before though?

 

[njparton]

Hmm, in fact my water seems to be getting even more alkaline... over 7.5 now...

Any ideas?

Then you have some carbonate in there, somewhere. What sort of gravel or sand do you have?

No sand, just gravel. Can't tell you preceisly what it is but it "passed the acid test"....

The only other recent changes were to add some more plants and as the only substrate I have is the gravel I've added some root tablets - maybe that's the cause?

You can definitely see the brown tanin in the water now, but the pH is still going up

 

[njparton]

I added some "Root Tabs plus Iron" by Aquarium Pharmaceuticals to be exact. They contain "potassium, magnesium, sulphur and iron and First Layer Pure Laterite."

http/wwww.aquariumpharm.com/aqplant.html

 

[Alien Anna]

Then you have some carbonate in there, somewhere. What sort of gravel or sand do you have?

No sand, just gravel. Can't tell you preceisly what it is but it "passed the acid test"....

The only other recent changes were to add some more plants and as the only substrate I have is the gravel I've added some root tablets - maybe that's the cause?

You can definitely see the brown tanin in the water now, but the pH is still going up

It can't be the root tabs but maybe only some of your gravel is limestone or carbonate, so didn't react in the test? KH and pH can't come from nowhere so if its going up, its coming from somewhere. Most likely a mineral.

 

[Lateral Line]

>>> I was thinking the iron LOWERED my pH before though?

Iron neither raises or lowers pH. pH is a measure of the Hydrogen ion concentration. As Anna has said, if your pH is rising, something is making it do so, and the most common source is some kind of Calcium or Magnesium Carbonate, (or a mixture, Dolomite for example).

You have no other rocks in your tank?

 

[njparton]

>>> I was thinking the iron LOWERED my pH before though?

Iron neither raises or lowers pH. pH is a measure of the Hydrogen ion concentration. As Anna has said, if your pH is rising, something is making it do so, and the most common source is some kind of Calcium or Magnesium Carbonate, (or a mixture, Dolomite for example).

You have no other rocks in your tank?

No other rocks.

The only 2 recent things I've done is remove a piece of slate and replace it with bogwood.