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Still very confused about KH and active substrates

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Hi guys,

Can anyone please explain to me the importance of KH in planted tanks and how it works with active substrates? I'm aware that KH buffers pH, and often in the shrimp keeping hobby people say you should keep KH at 0-1 so the buffering capacity of the substrate is not consumed.

Basically my questions are as follows:

1. Is lack of KH going to be detrimental to a planted tank?
2. Is lack of KH going to cause wild pH swings when co2 goes on/off and harm any livestock I add?
3. Is having higher KH (4 for example) going to deplete anything in the soil other than its buffering capacity? How would this affect pH etc.

I'm wondering whether it's better for me to have some KH, or have no KH. This particular tank probably isn't going to be housing any shrimp that require the lower pH.

If anyone can clear up my confusion I'd be very grateful :wacky:

Chris
 
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dw1305

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Hi all,
Have a look at <"Long term substrate">. Cherry Shrimps don't like really soft water, and neither do some plants, Vallisneria is the one I can't grow in the tanks but grows like a weed in our tap water (about 17dKH).

cheers Darrel
 

Iwagumi_Scaper

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Hi all,
Have a look at <"Long term substrate">. Cherry Shrimps don't like really soft water, and neither do some plants, Vallisneria is the one I can't grow in the tanks but grows like a weed in our tap water (about 17dKH).

cheers Darrel


Hi Darrel,

I'm struggling to make sense of it all if I'm honest ha. So my tank parameters at the moment are TDS 200, KH=0, GH=7-8. Is this OK for plants and livestock or am I going to have serious problems with pH swings with my co2 injection?
 

dw1305

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Hi all,
Hi Darrel,
I'm struggling to make sense of it all if I'm honest ha. So my tank parameters at the moment are TDS 200, KH=0, GH=7-8. Is this OK for plants and livestock or am I going to have serious problems with pH swings with my co2 injection?
The explanation <"needs a bit of chemistry">, but the simple answer is that you can ignore the <"pH drop caused by adding CO2">. The only real exception to this is if you <"have snails that need hard water">, as they will suffer from <"shell attrition"> whilst the pH is under pH7 (the "shell attrition" link also covers dKH/dGH).

Personally I like a bit of dKH, I use rain-water in the tanks, but we have hard tap water, so I just use a bit of tap to cut the water when the conductivity (TDS) has dropped. Hard water in the UK adds 1dKH for every 1dGH, because both are derived from the limestone (CaCO3) dissolved in the water.

You have a difference between the dKH and dGH in your tank water because you've added "salty shrimp mineral GH" salts that just raise the dGH (most <"calcium compounds aren't soluble">, so whatever the web site may say the dGH source is almost certainly calcium chloride (CaCl2).

For keeping Cherry Shrimps, I wouldn't use the Salty Shrimp at all. I'd just cut the RO with some tap water. If you have an "active substrate" it will exchange H+ ions in the substrate for Ca++ ions in the tank water. The more Ca++ ions you have the more quickly an equilibrium will be reached between the Ca++ ions in the substrate and water (this is what has happened when the substrate is no longer "active").

cheers Darrel
 

Iwagumi_Scaper

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The only real exception to this is if you <"have snails that need hard water">, as they will suffer from <"shell attrition">

I do intend on keeping a single Horned Nerite snail in the tank. It's just going to be a small school of maybe 5x Endlers Livebearers. Does having KH in the water get neutralised by the substrate? So if I set my water to a KH of 4, will the substrate not consume that and try to bring it back down to KH0? I'm just wondering what's going to be best for me in terms of healthy plants, snails and fish.
 

Iwagumi_Scaper

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Why dont you just use tap water as it is? or have I missed the reason why your using RO water!

Things that I've read had led me to believe that KH was a no no with active substrates and that it will always fight against itself to bring the KH right back down again so I thought I'd get more pH problems than if I used RO :/ I don't rly know why.

If it's fine and stable then I'll probably switch to a 50/50 tap/RO mix as my tap has pretty high KH/GH as standard. If I switch back should I do it gradually with a few water changes?
 

Iwagumi_Scaper

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Well my RCS dont have an issue with my tap water, plus the guy whom I got my dennerle scapers tanks from lived a short distance from York train station he was using tap water had his scrimp was fine too.

It probably won't even be a shrimp tank to be honest.

Do you use ADA Aquasoil? There are some old forum posts from like 2007 that say carbonate hardness with ADA Aquasoil makes the soil turn to mush and the water permanently cloudy. Is this from a previous version of the substrate that has now been corrected do you think?
 

dw1305

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Hi all,
Things that I've read had led me to believe that KH was a no no with active substrates and that it will always fight against itself to bring the KH right back down again so I thought I'd get more pH problems than if I used RO .
The active substrates work by "ion exchange", it just means that the harder the water is the more quickly the exchange sites will fill up with Ca++ and HCO3- ions.

Have a look at <"Questions about substrate.."> (the whole thread is relevant).
If it's fine and stable then I'll probably switch to a 50/50 tap/RO mix as my tap has pretty high KH/GH as standard. If I switch back should I do it gradually with a few water changes?
Yes I'd probably try and avoid any sudden big changes in water chemistry.

I don't measure anything other than the conductivity, and even that I do infrequently. My suggestion would be get the plants growing well, and the livestock looking happy, and then take a "datum" conductivity reading (TDS measurements are the conductivity in microS multiplied by 0.64) then just use your water changes (mix RO and tap) to maintain the conductivity somewhere near that value.

I keep the water in a range of about 50 microS either way of the datum (datum is about 110 microS, so 60 - 160 microS range, but your initial datum will be higher). Have a look at <"A simple continuous.....">.

cheers Darrel
 

Iwagumi_Scaper

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The active substrates work by "ion exchange", it just means that the harder the water is the more quickly the exchange sites will fill up with Ca++ and HCO3- ions.

Thanks for the info Darrel. I'm going to do another 50% water change tomorrow with either a 50/50 RO/Tap or just straight tap depending on how the tests come back. From what I understand the substrate will drag down the KH and GH slightly so I should take that into account and add water that's a bit above the target values I'm after?
 

Iwagumi_Scaper

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maintain the conductivity somewhere near that value

Hi Darrel,

My water straight out of the tap is KH7 and GH 18 approximately. This should be perfect when added to the tank right? So if I just make sure the TDS is the same each time by adding/not adding RO I should be ok?
 

dw1305

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Hi all,
This should be perfect when added to the tank right? So if I just make sure the TDS is the same each time by adding/not adding RO I should be ok?
Yes, just some-where in the ball-park, @Zeus. might be able to tell you what plants/fish have done well for him in similar water.
My water straight out of the tap is KH7 and GH 18 approximately.
That is quite unusual, are they the figures from the water company? or are they via a test kit?

Theoretically there isn't necessarily a link between dGH and dKH, for example sodium bicarbonate (NaHCO3) raises dKH but not dGH, and calcium chloride (CaCl2) raises dGH but not dKH, but in practice in the UK both values tend to be the same because the hardness is derived from CaCO3, which goes into solution as Ca++ and 2HCO3-.

Whatever the exact figures are doesn't make a huge amount of difference, the water is "hard" and I would expect the TDS straight out of the tap to be ~350 - 450ppm. If you cut the tap 1/2 and 1/2 with RO you will half that TDS value. If your TDS value creeps up over time (from the fertiliser addition) you probably need to change a bit more water.

cheers Darrel
 

Zeus.

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Yorkshire water quality reports

Iwagumi_Scaper
upload_2018-8-16_21-9-39.png


Zeus
upload_2018-8-16_21-8-11.png


Not that recent but.....................
 

Iwagumi_Scaper

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Just done mine with my Hanna pen and I got 411ppm for my tap water

Looks like mine is fine for most things then. I'll start with a 50% water change tomorrow using tap water and test the tank water in the evening. I do have a Nerite Snail arriving so I hope it'll be OK.
 

Zeus.

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Just tested my tank water after a week of ferts EI dose at 200% and 560ppm, first time I have really used the TDS/ppm meter on the pen, I just accept the hardness and see how the plants do ;) but using RO water with needing 250l WC a week would be a real pain storage and would use so much water running the RO unit.
 
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