Hi there. My tap water kh is virtually zero. Up to now I've been using liquid carbon but I want to go onto a pressurised cylinder. Now I know that kh has to be at least 4 to avoid ph drops but I wondered what's the best way to buffer my tapwater?Remember I do 50% water changes a week in accordance with ei. Is it best to use a kh buffer or maybe mix some coral gravel into my aquarium gravel. If anyone has low kh tapwater like me please can you give me some advice on the best way to get my kh up to at least 4?
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extremely low kh in local tapwater
- Thread starter mike b
- Start date
Hi all,
You can have water with any dKH value <"Wanted: pictures of tanks ........">, it is only in the drop checker that you need to know the solution is 4dKH solution <"CO2 measurement using a drop checker">.
In really soft water it is impossible to obtain pH stability. Have a look at <"What is worse: permanently high CO2 or dramatic pH swing?">
If you want to raise your dKH you can use an aragonite source of carbonate (Oyster Shell Chick Grit is the cheapest option and more environmentally friendly than coral gravel) or you can use potassium bicarbonate (KHCO3), which is soluble.
Using potassium bicarbonate - 1.8g KHCO3 in 25 litres of water = 2 dKH, (from <"James' Planted Tank - Remineralising Agent for RO Water">.
cheers Darrel
You can have water with any dKH value <"Wanted: pictures of tanks ........">, it is only in the drop checker that you need to know the solution is 4dKH solution <"CO2 measurement using a drop checker">.
In really soft water it is impossible to obtain pH stability. Have a look at <"What is worse: permanently high CO2 or dramatic pH swing?">
If you want to raise your dKH you can use an aragonite source of carbonate (Oyster Shell Chick Grit is the cheapest option and more environmentally friendly than coral gravel) or you can use potassium bicarbonate (KHCO3), which is soluble.
Using potassium bicarbonate - 1.8g KHCO3 in 25 litres of water = 2 dKH, (from <"James' Planted Tank - Remineralising Agent for RO Water">.
cheers Darrel
Ok so say I use oyster shell in my tank to raise the kh to 4 (I know it can be higher but I will use 4 as an example) and I do a 50% water change with my tapwater that has a kh of approx 1 (I'm being generous saying 1. It is that low) would that kill off my livestock? I know oyster shell is slow acting and doing a 10% change wouldn't make any difference but a 50% would?
Chris Jackson
Member
hi, well i'm in Cornwall with extremely low KH that measures nil with a test kit. I simply add bicarbonate of soda from a supermarket to get a KH of 5. Have done it for years with no problems and you soon get to used to getting the dose right.
Edvet
Member
Be glad, it's far easier and cheaper to get KH up than down
Chris Jackson
Member
Oh really, no, I've not found that at all. I'm on 50% changes weekly and the tank holds pretty steady in the 4-5 range.
Hi all,
This isn't as relevant for planted tank keepers, and if you are changing 50% of the water every week, its just not going to happen. There is an explanation at the excellent <"Skeptical aquarist - Bio-acidification">.
That is also one advantage of the coral gravel/shell grit approach, you have a reserve ("buffer") of "insoluble" CaCO3.
Hope that makes sense.
If you are using EI you can just add KHCO3 with the rest of your salts. 3.6g KHCO3 in 25 litres is 4dKH.
cheers Darrel
No, it should be fine, you will still get relatively slow changes in water chemistry. HCO3- is a "weak base", and in equilibrium with CO2 (as H2CO3-) a weak acid, so this is a "buffered system".
Sodium bicarbonate (NaHCO3) works just as well to raise dKH. The only reason for preferring potassium bicarbonate (KHCO3) is that the potassium ion (K+) will be taken up by the plants, whilst the sodium ion (Na+) won't. This is why the sea is salty with 99% NaCl, plants don't have much requirement for either Na+ or Cl- ion so they have a very long residence time in the sea water.
You can exhaust the HCO3- ions, it is because NaHCO3 full disassociates, so you have no reserve of ions (the system isn't "buffered").
This isn't as relevant for planted tank keepers, and if you are changing 50% of the water every week, its just not going to happen. There is an explanation at the excellent <"Skeptical aquarist - Bio-acidification">.
That is also one advantage of the coral gravel/shell grit approach, you have a reserve ("buffer") of "insoluble" CaCO3.
Hope that makes sense.
If you are using EI you can just add KHCO3 with the rest of your salts. 3.6g KHCO3 in 25 litres is 4dKH.
cheers Darrel
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Chris Jackson
Member
Thanks Darrel, very intersting.
Excellent explanation Darrell. Really interesting. Seeing I'm dosing ei anyway it seems that potassium carbonate might be the way to go. You say 3.6 gram per 25 litres of water. I know everything ei is estimated but what would 3.6 grams equate to? Half a teaspoon, a teaspoon more? Sorry I'm not up on grams.
