PH/KH in my 30g

[Sparx]

All this chatter about PH swings in other members tanks has me a little concerned for my own..

I’ve been using strip tests since I got the tank in January and everything had always been fairly normal with no worries. I recently bought a liquid test kit as on here everyone recommends them for being more accurate than the strip tests. So I went out and got one. I tested both tanks today.

10g Tank:
Ammonia: 0.0
Kh: 3
Nitrate: 10.0
Nitrite: 0.0
Ph: 7.5

30g Tank:
Ammonia: 0.0
Kh: 13
Nitrate: 10.0
Nitrite: 0.0
Ph: 8.5

First thing I thought was, ooo that Kh/ph is a lot higher than I thought it was in the 30g, a lot higher than what the strips were reading.
I did another strip test just to compare and it showed Kh as 6 and ph as 7.2 in the 30g.
Also the liquid test did not come with a solution to test GH but I believe it’s around 14 (if the strips are correct that is!)

I’ve read up that high Kh can cause high ph and that it can have a negative effect on plants.. which kinda makes sense because my amazon swords are still insisting on going brown.

Now, do I have anything to worry about here? Should I try bringing the the Kh/ph levels down to a more neutral level? What can I do to accomplish this? Unfortunately I don’t have any means to filter the tap water for RODI so is there an alternative?

 

[Colin_T]

Test the tap water to find out if the KH is coming from the water supply or something in the 30g tank that is increasing the KH and pH. Post the results here.

edited to fix a typo, should have been if and I put it

 

[MaloK]

You would need to test your source water before, to be able to compare. Then you may want to test if it is not something in the tank that cause your hardness increase.

I lived in a city that had super soft water during the day and that was switching to hard water during the night.

Once I found that out, I knew when to take the water to have the chemistry I wanted.

 

[Sparx]

Test the tap water to find out it the KH is coming from the water supply or something in the 30g tank that is increasing the KH and pH. Post the results here.

You would need to test your source water before, to be able to compare. Then you may want to test if it is not something in the tank that cause your hardness increase.

I lived in a city that had super soft water during the day and that was switching to hard water during the night.

Once I found that out, I knew when to take the water to have the chemistry I wanted.

Well, I’ve just tested the tap water, and the Kh is 15! What do I do with that? more tap water conditioner?

And this now brings me to another question.. how come the Kh in the 10g is 3??

 

[MaloK]

How long has the tank been established ? And what is your current water change schedule ?

 

[Sparx]

@MaloK
The 30g (with the big Kh) has been established since January of this year.
The 10g (with the low Kh) has been established for about a month, if that.
Both tanks have live plants in them if that makes a difference at all.
*edit to add*
Water changes are carried out once a week in both tanks, it’s water change day today.

 

[Colin_T]

Maybe a faulty test on the smaller tank.

If you want to drop the KH, you can mix the tap water with rain water, distilled water or reverse osmosis water. A 50/50 mix would give you a KH around 7.5dGH.

 

[Sparx]

Maybe a faulty test on the smaller tank.

Surely not? It’s the same solution same bottle, same liquid, same test tube. Just different tank water

 

[hamfistUK]

Well, I’ve just tested the tap water, and the Kh is 15! What do I do with that? more tap water conditioner?

And this now brings me to another question.. how come the Kh in the 10g is 3??

My guess is that you have an active substrate in the 10g, absorbing the carbonates (KH). These are designed to absorb all carbonates (KH) and buffer to a pH in the 6's. I suspect you are overwhelming its buffering capacity with your super high KH water, hence it is not absorbing all the KH. Be aware that these substrates will completely stop lowering KH once this buffering capacity is used up - and as you are adding 15dKH tap water for water changes that may not be too much longer. Keep an eye on it, because the KH will swing up at some point when the buffering is exhausted. I doubt it will be quick enough to be dangerous in the short term but it may affect the long term health of fish and plants.

 

[Sparx]

My guess is that you have an active substrate in the 10g, absorbing the carbonates (KH). These are designed to absorb all carbonates (KH) and buffer to a pH in the 6's. I suspect you are overwhelming its buffering capacity with your super high KH water, hence it is not absorbing all the KH. Be aware that these substrates will completely stop lowering KH once this buffering capacity is used up - and as you are adding 15dKH tap water for water changes that may not be too much longer. Keep an eye on it, because the KH will swing up at some point when the buffering is exhausted. I doubt it will be quick enough to be dangerous in the short term but it may affect the long term health of fish and plants.

Ooooooh The substrate hubby bought for the 10g apparently has nutrients and is good for plants etc so could well have some form of active ingredient which is lowering the kh and that would make complete sense. I wouldn’t know without checking the bag but I bet you’re right.
Thanks for the heads up, I will keep an eye one it. Thank you