Tried to adjust KH but didn't budge

[Iwagumi_Scaper]

Hi all,

So originally I had water in my tank of KH 0 because I incorrectly thought I should be using RO and mixing to this level. I tried to bring this up to around KH 3-4 by using water out of my tap (KH of 7) and doing a 50% water change, but my test kit still says the KH is 0-1.

How does mixing water work with regards to KH? I though by using my tap water and a 50% water change that the KH measurement would change to around 3.5 or 4

 

[ian_m]

Most hobby test kits will not reliably read below 8KH, (though some are 4KH) so resulting water may probably be 4KH but is untestable with hobby grade test kit.

https://uk.hach.com/total-hardness-test-kit-model-5-b/product-details?id=25114234042&callback=pf
Here is a test kit that will work down to 1 gpg (1KH).

Why are you using RO water when at 7KH your water is gorgeously soft and many fish keepers would die to have water like this ?

 

[Iwagumi_Scaper]

Why are you using RO water when at 7KH your water is gorgeously soft and many fish keepers would die to have water like this ?

Was advised by the guys at a very well known aquascaping specialists to aim for a KH of no less than 3 and no more than 5 so that's what I'm aiming for. My tap water seems to vary a LOT week to week. Last week it was 7KH and 381 TDS, today it's 4KH and 208 TDS. I don' really want the parameters fluctuating up and down :/

Most hobby test kits will not reliably read below 8KH

I use this kit to test the water for my other shrimp tank downstairs and it's worked to 3-4 KH in the past so I think it's fairly accurate. The guys I spoke with did say tthat my substrate will pull it down by ~1 degree so maybe it's fine after all. If I make sure I make it up to 4KH every time it should be spot on.

 

[ian_m]

Clearly you have some source of error, my bet is test kit misreading below a certain KH value or some other interfering ion cause a false reading.

If you insist on going to all the effort of RO, despite soft tap water, I would just mix RO:tap 50:50, everything will be fine. Fish happy, shrimp happy & plants happy.

If using CO2 low KH just makes things more "knife edge" to asphyxiating your live stock.

I don't really want the parameters fluctuating up and down :/

Of course you will get major parameter swings at water change time, fish & plants don't really care provided temperatures and parameters are approximately the same in magnitude.

 

[dw1305]

Hi all,

How does mixing water work with regards to KH? I though by using my tap water and a 50% water change that the KH measurement would change to around 3.5 or 4

Yes, it should be half of the dKH of the tap water.

I agree with @ian_m, it could be the test kit, it depends on what the kit measures. If it measures alkalinity, rather than carbonate hardness? It could be because of cation exchange, with a Ca++ ion being exchanges for a H+ ion from the substrate. If the pH hasn't changed after the addition of the tap water it is ion exchange.

Was advised by the guys at a very well known aquascaping specialists to aim for a KH of no less than 3 and no more than 5 so that's what I'm aiming for. My tap water seems to vary a LOT week to week. Last week it was 7KH and 381 TDS, today it's 4KH and 208 TDS.

They don't really matter as fluctuations, if you think of the water in streams etc. its chemical composition will vary from week to week, dependent upon rain-fall etc.

We have a small spring fed stream on the University campus. It is always alkaline (the geology is all calcareous inter-bedded limestone and clay), but the conductivity will vary between 300 - 700 microS dependent upon how much it has rained before you sampled it.

If you get tap water from a deep aquifer it will be fairly consistent, but not otherwise.

cheers Darrel

 

[Iwagumi_Scaper]

They don't really matter as fluctuations, if you think of the water in streams etc. its chemical composition will vary from week to week, dependent upon rain-fall etc.

Everything I've read about shrimp/fish keeping has been "make sure kh, gh and tds are the same for water changes". Are you saying that TDS/KH and GH creeping up or fluctuating up and down will do no harm to the livestock in the tank? :/ I've always thought stable parameters were one of the most important things in an aquarium.

 

[dw1305]

Hi all,

Are you saying that TDS/KH and GH creeping up or fluctuating up and down will do no harm to the livestock in the tank?

Generally yes.

There are provisos. It depends a little bit where livestock come from. If you keep Lake Tanganyika cichlids they inhabit a lake which is 30,000,000 years old, near the equator and that contains a huge volume of, very carbonate rich, water, and they don't have much environmental tolerance. Black-water fish would be another example, but at the opposite end of the carbonate hardness spectrum. To lower the pH of Tanganyikan water you need to add a lot of acid, in a black water tank, with water with 0dKH, any addition of acid, however small, will lower pH.

I haven't kept Crystal Red Shrimp, but I believe they are quite delicate. I have kept Red Cherry Shrimp and they are pretty tolerant as long as the water doesn't get too soft.

I've always thought stable parameters were one of the most important things in an aquarium.

For me probably, in order, adequate oxygen levels, actively growing plants and a varied diet.

I don't like rapid changes in water chemistry, but is there a difference between 3dKH and 5dKH? Not really. The same with ppm TDS, you had ~180ppm TDS difference, which is quite a large number, but it is still a small amount of salts.

I'll do it as conductivity (100 microS = 64ppm TDS), so call 180ppm TDS a ~300 microS difference. <"Half a gram of salt (NaCl), in one litre of water">, will raise the conductivity by 1400 microS, and we have ~1/4 of that rise, so the difference in salt (as ions) content is equivalent to less than 1/8 gram of salt per litre.

cheers Darrel