Help please! Mature tank KH & PH issues

[Aquanut]

Dear community,

I have a fluval flex 123 litre tank which has been running for around 18 months now. It is fully planted with a fairly large piece of mopani. All the fish are happy in a soft acidic environment so i was not too concerned with PH of 6.4 a few weeks back. This tank is beautifully over filtered as standard & i have a seperate internal UV filter with venturi running as well

The tank gets a 25% water change fortnightly, the gravel is vacuumed as best as possible. all the fish are healthy & happy. I was running 50/50 RO/Tap but on noticing low KH started leaving the RO out & just using tap. Here in Norfolk UK the tap water is liquid rock, super hard.

I thought that maybe the trumpet snails were stripping carbonates out? 

I am having real problems with KH & PH. The KH is 0 & the PH is around 6.0. I have tried adding seachem equilibrium to get the KH up but i think i could add tubs full & get nowhere. I did a tap only 50% water chage which brought the KH & PH up to nicer levels but within a few days both were back to low levels with KH at 0. I am concerned with no KH the PH can swing wildly but thankfully all fish are healthy & not stressed.

At this point i am considering the only solution being to strip the tank down, throw away the substrate which is 2.5 inches of aquasoil topped with a half inch of gravel. Thus getting rid of the snails. I can’t think of another way but am reluctant due to the beautiful mature swords & lotus.

So here i am reaching out to you guys for help, all suggestions will be gratefully received. I’m sure i have left out some technical details that may be required for a reasoned response so please ask anything.

I would rather avoid having to add vast quantities of chemical.

Many thanks for reading this post.

 

[Mmiller2001]

Equilibrium is only for GH and adds some amount of K and Fe. This is why you are still seeing 0dKH. I recommend grabbing this: https://www.amazon.com/gp/product/B074D9BXRT/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

You can add it directly to the tank and adding 3.03g to your 123L will raise KH by 1dKH. This will also add 13.93ppm K to the tank as well. Keep that in mind.

Hope this helps.

Edited July 19, 2021 by Mmiller2001

[Hobbit]

@Mmiller2001 is there a reason you prefer potassium carbonate over calcium carbonate? I assume in this case it’s because the GH is already high?

@Aquanut depending on what kind of aqua soil you have, it could be designed to strip the KH from the water and keep your pH low. A friend gave me some Fluval stratum a year ago and I just this week figured out it actively lowers KH. 🤦🏼‍♀️ That’s not to say the KH is totally absent or useless though—it’s my understanding the stratum “holds” it until it’s needed. @Mmiller2001 knows way more about this than I do, so he can correct me if I’m wrong.

[Perry]

Hi @Aquanut, firstly I'd say don't panic and tear down your beautiful tank; especially since your fish aren't showing any signs of stress. As @Mmiller2001 mentioned above the Equilibrium only raises GH. There are seachem additives designed to adjust the KH but I think you'll find that adding a bag of crushed coral to your filter is a simple, gentle way to raise your KH enough to stabilize your pH. I hope you find something that works for you and your tank.

[Mmiller2001]

On 7/19/2021 at 7:35 AM, Hobbit said:

 is there a reason you prefer potassium carbonate over calcium carbonate? I assume in this case it’s because the GH is already high?

It will increase GH. By using potassium carbonate or potassium bicarbonate, GH is unchanged.

[Aquanut]

GH is 19 degrees.

I take it adding crushed coral will increase GH as well?

where as adding potash will not increase GH but will increase potassium?

Edited July 19, 2021 by Aquanut

[Hobbit]

On 7/19/2021 at 10:03 AM, Aquanut said:

I take it adding crushed coral will increase GH as well?

where as adding potash will not increase GH but will increase potassium?

Yep!