KH & pH drops

[Jman17H]

I have been fighting my 20 gallon for the last several weeks.

Specs:
2.0 wpg T-12 flourescent
2-2 liter DIY CO2
Amazon Swords, Ludwigia brevipes & bacopa caroliniana
no driftwood or rocks
mix of Schultz's & sand as substrate
HOB filter with aquaclear sponges
Blue mystery snails, MTS and ramshorns snails only w/ no fish
Dose flourish and potassium weekly (not EI method)
It is supposed to be my low maintenance tank

It seems that for some reason the KH has been dropping to 0 thus making the pH drop to 6.0 or below. I add baking soda and without major shocks can get it back to a KH of maybe 2 and pH of 6.4 (my reading last Sunday) but in less than a week the KH and pH have dropped all the way down again? What is the problem and what can I do so my KH does not keep plummetting?

 

[SparKy697]

Can you tell us what your water parameters are out of the faucet? KH, GH, and pH?

 

[Zezmo]

What is Schultz's?

Some substrates can consume your Kh.

 

[Jman17H]

Tap water stats:
pH = 6.4 (It must vary for I know it was 7.0 a few months ago)
KH= 2
GH = 8

Schultz Aquatic Plant soil: Found at Home Depot http://www.schultz.com/ProductCategories/Soilsamendments/AquaticPlantSoil/
It basically looks a lot like flourite but is an inert fired clay. I have used it in prevoius setups and never had a KH drop problem.

I am not a believer in the EI method so I only do water changes about once a month. I do weekly testing instead to keep up with phosphates and nitrates. My other 2 planted tanks do not drop KH but they both have heavy fish stocks with lots of driftwood and rock formations and 4.0+ wpg of light and good amounts of CO2 (30L has DIY while 150 has pressurized).

I am basically just using this tank as a snail and plant tank and I can keep adding baking soda every week to maintain the KH but would rather fix whatever problem I have?

 

[Purrbox]

Some plants can also breakdown the KH to make use of the carbon if the CO2 levels are not high enough. The snails will also remove calcium from the water column for their shell growth, although this should affect the GH and not the KH.

You could try adding some crushed coral to your filter to help buffer the KH and GH so that you don't have to make weekly additions of baking soda. Another option would be to up your waterchange schedule to once a week so that your KH and GH are replenished by the tapwater supply.

 

[SparKy697]

Some plants can also breakdown the KH to make use of the carbon if the CO2 levels are not high enough. The snails will also remove calcium from the water column for their shell growth, although this should affect the GH and not the KH.

You could try adding some crushed coral to your filter to help buffer the KH and GH so that you don't have to make weekly additions of baking soda. Another option would be to up your waterchange schedule to once a week so that your KH and GH are replenished by the tapwater supply.

I'm only figuring all of this out myself but it looks like your water has little ability to buffer against change. KH is only 2 right from the tap so even PWC may not do that much for you. Coral would surely be a good thing to try. I have a 10 gallon that is just for snails and I had to resort to coral because the calcium was all but being used up. I actually went to a coral substrate to see how that does.

Purbox, if most of his GH is from calcium, would he benefit from adding other minerals to keep GH from dropping so low?

 

[Purrbox]

Crushed Coral contains both calcium and carbonates which is why it buffers both KH and GH. There are other chemicals that can be used which will provide the same function. I recommended the Crushed Coral since it would solve the problem of having to make weekly additions of the baking soda.