# Can old tropica soil exposed to hard water raise the KH of soft water?



## rubadudbdub (27 Sep 2020)

Hi folks
I have a fluval spec 19l set up about 18m ago with tropica soil.  Tap water is pH 7.5, kH 4-5, gH 8, which has been used in the tank since it was set up.    Tank water recently had gH up at 15.  Not sure if it was ferts and lack of water changes, or maybe some crypt melt (possibly from the rain water) releasing ions raising GH?

I wanted to keep some killifish (and play around with rain water) so  have been doing water changes with rain water to lower kH and GH.   I've also got an almond leaf and some alder cones in  the tank. 

Yesterday after a water change kH was 1-2,  next day its back at 4.  

Can the buffering action of tropica soil work the opposite way?  Ie into a water column with low KH release bicarbonate (I presume) from an old soil that's ability to buffer to a lower pH has been exhausted?


I should perhaps stop thinking about this as from reading about the F gardneri 'misaje' I picked up, they'll probably be happy with kH of 4.    Covid induced boredom is making me wonder about these things


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## Nick potts (27 Sep 2020)

rubadudbdub said:


> Can the buffering action of tropica soil work the opposite way?  Ie into a water column with low KH release bicarbonate (I presume) from an old soil that's ability to buffer to a lower pH has been exhausted?
> 
> 
> I should perhaps stop thinking about this as from reading about the F gardneri 'misaje' I picked up, they'll probably be happy with kH of 4.    Covid induced boredom is making me wonder about these things



I am not 100% sure on the first question but I think the answer is no. I'll let someone with more experience chime in.

As for the fish, I think that stability is what you need more than the "perfect"  KH, your tap water looks like it would be perfectly fine for the killifish


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## dw1305 (27 Sep 2020)

Hi all, 





rubadudbdub said:


> Can the buffering action of tropica soil work the opposite way? Ie into a water column with low KH release bicarbonate (I presume) from an old soil that's ability to buffer to a lower pH has been exhausted?


It can, it is <"ion *exchange* capacity"> and which ions are exchanges is dependent on both how strongly bound they are (dependent on their valency) and <"their relative abundance in the water column and bound in the substrate">.

The first time I used <"Tesco Moler Clay Cat Litter"> I rinsed it in tap water (about 18 dGH/dKH) and it used to raise the dKH/dGH of the rain-water in the tanks. If you leave it outside in the rain for ~12 months until the smell is gone, it works as an active substrate and lowers dKH/dGH.

cheers Darrel


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## X3NiTH (27 Sep 2020)

I’ve had exactly this happen with Fluval Stratum, the water was mineralised with Salty Shrimp GH+ and the KH of the water for a long while was close to Zero (pH was regularly in the low 5s’ with co2 injection). This substrate is designed to reduce the KH of water to make it more suitable for crystal shrimp (low to zero KH encourages prolific breeding) it manages this through the mechanism Darrel has just described. The problem started when I accidentally overdosed micro (about 350ml of APFUK chelated trace into a 28L aquarium) via a perstaltic pump (1ml per min) which I forgot to switch off manually after a few minutes post water change, I noticed the mistake hours later when I saw the pump spinning and the pristine changed water was going green tinged, I thought I had rectified this mistake with multiple water changes, it was obviously not enough as over the next few days all the Epiphytes and stem plants started melting including java fern, it was a few days in when I ran some tests and found the KH near 20ish when it should be closer to Zero, over time the realisation was that the micro fertiliser was swapping out with the carbonates that had been absorbed over the length of time I had used the substrate in ultra low KH (I documented this near the end of my first Journal).

I gutted the tank and ditched the substrate.


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## sparkyweasel (28 Sep 2020)

I love inert substrates: nothing to go wrong.


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## rubadudbdub (13 Oct 2020)

Thanks guys. Apologies for the late reply.  Been busy at work.  

I was trying to approach the water conditions in the shop I bought them from (TA aquaculture), which was pH just under 6 and very soft.  I take the point that they'll probably be happy as the water comes out the tap.  

The F gardeneri misaje were not listening to Debbie at TA and have decided to spawn in the aquasoil, rather than in moss or a mop.  So far they've spawned a few times over the last 4-5 days and I've seen the odd egg that then disappears. I'm not sure if the eggs are being eaten or just blown around the tank by ongoing spawning.   Time will tell.   I've added a mop to see if they'll lay in something easier to harvest eggs from.


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