Help KH drift during RODI transition

[bradleysryder]

What could cause a tank with older aquasoil to have fluctuating KH readings if the hardscape is inert?


Background:
I have a 90p tank that's been established for a year next month, and the same Landen aquasoil has been in since the beginning with no new added (just root tabs). Until recently I have been using my tap water. In the beginning it buffered the KH strongly, but this dissipated after 3-4 months and the tank KH has hovered right around what it is out of the tap, which is 5 KH. I am using dragonstone and mopani wood, and I believe neither of them should have an effect on KH.

I recently decided to make the switch to RODI water, and I am remineralizing to 1.7 KH and 6 GH using APT Sky+. I always confirm the values in the batch before adding any to the tank. I am doing the transition slowly with daily 5 gallon water changes. I've been at this now for 14 days.

What's strange is if I measured the tank KH ~8 hours after the water change (usually measured toward the end of the photoperiod), it is around 2 KH the last several days. However, if I then measure KH the next morning, it is back up to 3. Not a huge swing, but pretty consistently there.

Is it expected that KH will drift in a tank under normal conditions, or is it possible the aquasoil is leeching carbonate back out in some way? I'm not sure whether it absorbs or just neutralizes carbonate with its acidic nature.

Thanks for any insights!

 

[Naturescapes_Rocco]

It could be releasing it somehow, that's true. Mostly it's absorbing it. Perhaps something in the dragon stone is leaching?

Why are you dosing KH with aquasoil in the first place? Just curious if you have a specific reason.
Most users here run 0KH tanks, using RO water and either aquasoil, or just not adding any KH upon water changes.

All my tanks use pure RO water, and I've never remineralized KH in any tanks without any ill effects.

Here's a good article from 2hrAquarist that explains not needing KH. At the bottom of the article he also shows a ton of tanks with no KH.

So, personally. I'd recommend slowly weaning off of your KH dosing altogether. It'll be more stable in the long run with fewer fluctuations for fish/plants/shrimp, too. But that's just how I'd do it, I know many others have success with KH tanks, too.

 

[bradleysryder]

Why are you dosing KH with aquasoil in the first place?

It's a good question, and now that you mention it I don't have a great reason. Previously I was under the impression KH mattered for shrimp but now I realize that's just GH, so I suppose going 0 KH would be a better move (assuming KH isn't leeching from something in the tank). Thanks for the perspective... I will likely use this bag of Sky+ I already bought, but perhaps migrate to just Sky in the future

 

[Kwyet]

It depends what kind of shrimp you keep. Neos do best with at least 3 dkH .

 

[bradleysryder]

It depends what kind of shrimp you keep. Neos do best with at least 3 dkH.

I have amano shrimp only

 

[Naturescapes_Rocco]

It depends what kind of shrimp you keep. Neos do best with at least 3 dkH.

I've kept and bred Neos in 0KH, with BDBS , for over a year now! Dennis Wong also keeps shrimp, even caridina, in 0KH, too.

 

[Naturescapes_Rocco]

Thanks for the perspective... I will likely use this bag of Sky+ I already bought, but perhaps migrate to just Sky in the future

Also if you ever want to make your own GH remineralizer, it's super easy to do and I can help you out! It can save you some serious $$ over time. See this post here.

 

[Kwyet]

I’m not surprised about the Caridina, but I am surprised the Neos are doing well.

 

[Dennis Wong]

I’m not surprised about the Caridina, but I am surprised the Neos are doing well.

Caveat - neos is such a wide category, sensitive strains could well need a more narrow parameter range.

But when it comes to cherry shrimp and similar, they have become so robust due to artificial breeding that their tolerance range is quite ridiculous by now.

I've seen reproducing colonies in 0KH, 2GH, TDS 50 tanks ( super soft side for water) and I've seen reproducing colonies in hard alkaline water, 16dGH 16KH TDS 400+ tank.

i've had colonies in both very soft and more alkaline water, but the key thing is that you can't directly transfer those grown in very soft water to the tanks with more alkaline water, they will die. Drip acclimatization doesn't work also. However, you can slowly transit a colony that grew up in soft water (and vice versa) to more alkaline water by slowing changing the parameters over many months. My colonies are around 8 years old by now - mostly bred in 0KH tanks.

I did testing on shrimps in earlier years just to see what parameters affected livestock. For some batches I raised the TDS to 1000ppm, for other batches I raised the GH from 3 to 15 dGH just to see whether it can cause any die-off. I did similar experiments with ammonia, pH etc. I posted once about it on social media and got accused of animal cruelty. However, the data set is quite useful. Since everyone has cull shrimps, its a good opportunity to test things out and see for yourself what has impact, or not. (spoilers, most parameters really don't matter)

What could cause a tank with older aquasoil to have fluctuating KH readings if the hardscape is inert?


Background:
I have a 90p tank that's been established for a year next month, and the same Landen aquasoil has been in since the beginning with no new added (just root tabs). Until recently I have been using my tap water. In the beginning it buffered the KH strongly, but this dissipated after 3-4 months and the tank KH has hovered right around what it is out of the tap, which is 5 KH. I am using dragonstone and mopani wood, and I believe neither of them should have an effect on KH.

I recently decided to make the switch to RODI water, and I am remineralizing to 1.7 KH and 6 GH using APT Sky+. I always confirm the values in the batch before adding any to the tank. I am doing the transition slowly with daily 5 gallon water changes. I've been at this now for 14 days.

What's strange is if I measured the tank KH ~8 hours after the water change (usually measured toward the end of the photoperiod), it is around 2 KH the last several days. However, if I then measure KH the next morning, it is back up to 3. Not a huge swing, but pretty consistently there.

Is it expected that KH will drift in a tank under normal conditions, or is it possible the aquasoil is leeching carbonate back out in some way? I'm not sure whether it absorbs or just neutralizes carbonate with its acidic nature.

Thanks for any insights!

Some carbonates could have binded to your substrate over time. After a water change, it also takes time for all the water to mix (for example layers in the substrate), if you are at borderline readings, small change may be enough to give a slightly different reading. Over time it should diminish if you are not adding any KH. As long as you are 2 dKH and below, soft water stuff should be fine, so I don't think its a big worry.

 

[bradleysryder]

I tried a larger 10 gallon change last night to see if I could make a dent, and the KH and GH stayed the same as before - 3KH 12GH (previous tap values in the tank were 5 - 6KH and ~17GH)...so I'm getting more convinced there is residual minerals in the tank. Not a totally bad thing, a slow transition is probably for the best, but an interesting phenomenon I didn't expect.

 

[JacksonL]

What test are you using for KH?
If it is a ‘drop’ style test, they can be pretty coarse, and the difference between 2dkh and 3dkh results could be tiny, or even just test noise.

 

[bradleysryder]

What test are you using for KH?
If it is a ‘drop’ style test, they can be pretty coarse, and the difference between 2dkh and 3dkh results could be tiny, or even just test noise.

Yeah, API drop test unfortunately. I am definitely mentally building in some noise. It seems to me drop size has an effect on the results, and the bottle tips they use don't provide the most consistent drops. Hard to tell exactly what's happening, but it's slowly trending in the proper direction so I'll just stay the course for now and trust I'll end up in the right spot...eventually?

 

[hamfist]

I have amano shrimp only

Amanos are completely happy with zero KH. Although, as always with shrimp, transition them as slowly as is practicable if its going to be a big change (like more than 3 degrees KH or 5 degrees GH(they seem less sensitive over GH changes)). For less than that a decent drip acclimation should be sufficient.