Tested all my tanks' GH and KH today

[boofeng]

So I finally tested all my tanks' GH and KH. Results first, and then some discussion.

Methodology

Test kit: recently opened API GH/KH test kit (drop test), expires 2018 and 2020.
Procedure: very clumsily, with each tank tested only once

Results

Tank: eremnopyge 45x30
Substrate: 1.5 to 2 inches of loose peat moss
dGH: 2 / dKH: 0

Tank: bitaeniata 45x30
Substrate: less than half inch Aquael fine quartz sand, extremely decayed Catappa leaves, peat granules above sand.
Additional remarks: loose peat in filter bag behind HMF filter, used to receive deionised water changes (stopped 3 months ago)
dGH: 3 / dKH: 0

Tank: Crenicichla 90x30
Substrate: just under 1 inch ADA Malaya, extremely decayed Catappa leaves, a lot of driftwood
Additional remarks: peat granules in filter bag behind HMF filter, used to receive deionised water changes (stopped 3 months ago)
dGH: 4 / dKH: 0

Tank: candidi 45x30 cm
Substrate: 1 inch thoroughly mixed 50/50 ADA Malaya and ANS bright sand
dGH: 6 / dKH: 3

Tank: diplotaenia 45x30 cm
Substrate: 1 inch loose peat moss capped with 1 inch gardening sand
dGH: 7 / dKH: 3

Tank: trifasciata/Abacaxis 90x40
Substrate: baked clay above LECA pellets
Remarks: more than one year old
dGH: 9 / dKH: 5

For reference, my tapwater was dGH 6 and dKH 6 from a long ago test. IIRC.

Discussion

From my results, it seems that having ADA soil or peat moss or decaying Catappa leaves in contact with the water column tends to bring dKH readings to 0 and dGH readings to 2-4. No wonder all the local apisto guys stick to ADA soil and Catappa leaves - they do seem to work!

The exception is the candidi tank, which has some ADA Malaya, but reads dGH 6, dKH 3. I'm guessing there aren't enough peat-like substances there (no Catappa, too little ADA soil) to capture the 2+ ions.

I also found that Ceratophyllum is a rather decent indicator of whether my water is good for apistos - they melt in all the tanks with "good" water parameters. Oh, except the bitaeniata tank. Somehow the hornwort does fine there although the water reads dGH 3 dKH 0. Help me figure this out, someone?

Sadly, I found out about all these only today. The candidi have spawned at least twice, and the diplotaenia once, with no fry to show for it. I only measured the peat-filtered water going into all my tanks, and assumed those parameters would hold in the tank. Seems like I have some mineral source in the substrate or earthenware caves pushing GH and KH, and by extension probably pH, back up. I've just put in filter bags of peat granules to those tanks and hopefully that works. I'll report back.

Lastly, the trifasciata tank reads high unsurprisingly because the substrate is baked clay made from construction site waste soil. I removed quite a few rusty nails, tile shards, and bits of broken concrete while prepping it for the tank. The plants seem to love it though, and the trifasciata spawn profusely there. I have CRS living in a breeder box there too - no problems.

All in all, a good evening of sleuthing and learning.

Cheers
Bufeng

 

[Mike Wise]

If it works for you and the fish breed, why change. As you found, T. candidi, A. sp. Abacaxis & A. diplotaenia require very soft/acid water for successful reproduction. Those tanks need some changes.

 

[boofeng]

If it works for you and the fish breed, why change. As you found, T. candidi, A. sp. Abacaxis & A. diplotaenia require very soft/acid water for successful reproduction. Those tanks need some changes.

Yes Mike indeed they do, and I'm going to see if adding peat moss will solve it - that seemed to work in the bitaeniata tank (it used to have bad water params before I started chucking peat granules about). So in love with peat moss right now!

 

[dw1305]

Hi all,

Yes Mike indeed they do, and I'm going to see if adding peat moss will solve it - that seemed to work in the bitaeniata tank (it used to have bad water params before I started chucking peat granules about). So in love with peat moss right now!

Conductivity is a pretty good indicator of how soft your water is. If you can get the water below 50 microS, any source of weak acids should lower the pH right down.

cheers Darrel

 

[boofeng]

Hi all, Conductivity is a pretty good indicator of how soft your water is. If you can get the water below 50 microS, any source of weak acids should lower the pH right down.

cheers Darrel

Thanks for the tip, Darrel. My conductivity is still far from that (TDS reading is 115-145) as I've been a little busy and unable to get my DI unit back up and running. I plan to add an RO stage to it before installing it at my new place. That'll be in January if all goes according to plan.

Recently I've also been testing water parameters at some local breeders using ADA soil. They get dGH 3-4, KH 0, pH 5 to 6+, TDS 200 to 700(!!). Which more or less confirms what Ted Judy said in Dave's "ok" thread - that GH and pH seem to matter a lot more than conductivity for spawning.

Based on that, I've considered just using water softening resin. It'll be a lot cheaper than deionised water. Plus, I can regenerate that stuff at home with just 10% NaCl solution. Whereas I can't buy concentrated acid to regenerate DI resin without a licence here.

Still, using low conductivity water does make pH management much easier, as you say. I'm weighing the pros and cons and if anyone has ideas I'd love to pick your brains!

 

[dw1305]

Hi all,

Recently I've also been testing water parameters at some local breeders using ADA soil. They get dGH 3-4, KH 0, pH 5 to 6+, TDS 200 to 700(!!). Which more or less confirms what Ted Judy said in Dave's "ok" thread - that GH and pH seem to matter a lot more than conductivity for spawning.

Based on that, I've considered just using water softening resin. It'll be a lot cheaper than deionised water. Plus, I can regenerate that stuff at home with just 10% NaCl solution. Whereas I can't buy concentrated acid to regenerate DI resin without a licence here.

Yes, conductivity isn't the most useful parameter, it is just the one that you can measure accurately with a simple dip meter. You can potentially have high conductivity due to ion exchange, even if the exchanged ions are H+ ions. "Regani" gives an explanation in <"700 litre Amazone">.

I think Ted has been using <"Sodium cycle Strong Acid Cation Exchange" (heading "water softener")> followed by an RO filter for difficult fish, but I wouldn't just go down the ion exchange route unless you have access to relatively cheap KCl?

The problem with sodium (Na) is that most soft water plants have very low tolerances to it.

Carbonate hardness (dKH) is largely unaffected by strong acid ion exchange (you have sodium or potassium (bi)carbonate, rather than calcium (bi)carbonate in your softened water).

cheers Darrel

 

[boofeng]

Hi all,

Yes, conductivity isn't the most useful parameter, it is just the one that you can measure accurately with a simple dip meter. You can potentially have high conductivity due to ion exchange, even if the exchanged ions are H+ ions. "Regani" gives an explanation in <"700 litre Amazone">.

I think Ted has been using <"Sodium cycle Strong Acid Cation Exchange" (heading "water softener")> followed by an RO filter for difficult fish, but I wouldn't just go down the ion exchange route unless you have access to relatively cheap KCl?

The problem with sodium (Na) is that most soft water plants have very low tolerances to it.

Carbonate hardness (dKH) is largely unaffected by strong acid ion exchange (you have sodium or potassium (bi)carbonate, rather than calcium (bi)carbonate in your softened water).

cheers Darrel

You’re a treasure trove of knowledge, Darrel.

Good to know soft water plants don’t do well with sodium. Is it the absolute quantity of sodium that matters, or the relative proportion of sodium vs potassium? (c.f. I often see calcium/magnesium ratios being talked about in the domains of agricultural soil, reef tanks, and also planted tanks, IIRC.)

I do have access to hydroponics grade KCl, and it’s not exactly cheap (approx. 15 USD/kg), but I figure I can dilute the waste brine for use as terrestrial plant fertiliser, so it’s not completely unfeasible.

About KH, yes I see how sodium/potassium ion exchange won’t do anything to remove the carbonate/bicarbonate ions. They will be used up if H+ ions are added though, right? E.g. via peat moss?

 

[dw1305]

Hi all,

Good to know soft water plants don’t do well with sodium. Is it the absolute quantity of sodium that matters, or the relative proportion of sodium vs potassium?

A combination of both, this is from Blumwald et al (2000) "Sodium transport in plant cells":

Salinity imposes two stresses on plant tissues: (1) an osmotic water-deficit that results from the relatively high solute concentrations and (2) ion-specific stresses resulting from altered K+/Na+ ratios and Na+ and Cl− ion concentrations that are inimical to plants.

About KH, yes I see how sodium/potassium ion exchange won’t do anything to remove the carbonate/bicarbonate ions. They will be used up if H+ ions are added though, right? E.g. via peat moss?

Yes, you can remove dKH via acid addition, or <"anion exchange">.

Calcium carbonate (CaCO3) is insoluble in water, but soluble in weak acids. Because pure H2O dissolves a small amount of CO2 (and a small proportion of this CO2 becomes H2CO3) it is a weak acid and will gain dKH from "insoluble" carbonate rocks.

In solution CO2, carbonate, bicarbonate, carbon dioxide, and carbonic acid (H2CO3) form the TIC (Total Inorganic Carbon) and exist together in a dynamic equilibrium.

When you add pressurised CO2 to a system (like aquascapers do to get to ~30ppm CO2) you get a reduction in pH, but no change in dKH, when you add an acid (H+ ion donor) you get a reduction in dKH, followed eventually by a reduction in pH.

cheers Darrel

 

[boofeng]

Hi all

Thanks everyone, for all the help and info.

A little update with a happy ending - I have spawns! It's the diplotaenia and eremnopyge, free swimming fry emerging two days apart. After the series of tests in the original post, I dropped nylon stockings full of peat moss in a few tanks. I maintained a regime of peat filtration but stopped checking water parameters due to illness and work. The water got really brown.

I do poke the TDS meter around a bit. Interestingly, my tapwater's TDS reading is coming down gradually, from 120 ppm down to 85 this week (probably due to a recent rainy spell). Anecdotally, a lot of local fishkeepers claim spawning happens more in the rainy season (Nov, Dec, early Jan). They attribute it to lower temperatures, but it might just be purer water, I'm thinking.

Incidentally, the tanks are adjacent and the fish flare at each other often. Off-topic - but do people find that spawning fish encourage their neighbours to spawn as well? (Maybe a natural response to perceived competition?)

Sorry for the poor pics or lack thereof - the tanks are 15 cm off the floor (I stuck them on the bottom tier of a commercial tank stand) and I've not cleaned the panes or pruned plants for a long while. Lesson learned - tanks have to be at least 45 cm off the floor to be enjoyed!