[Chiefston]

Hey all,
So, I'm wondering does dosing EI (using Pfertz N,P,K and Flourish Comp) raise your KH and GH?
I have a 6gal Fluval Edge, and I do weekly 50% water changes with RO water. Before my water change, my readings were KH-7, GH-11. One day after the water change, my readings are KH-7, GH-9.
I do have Seriyu stones in the tank, and have high CO2 (yellow drop checker). I understand this will raise KH, but I don't believe it should raise it so quickly, and that does nothing to explain the rise in GH.
Any ideas? :help:

 

[Diana]

GH of 9-11 is pretty hard water, highly suited to live bearers, certain rainbow relatives, snails and a few shrimp. It is at the high end of OK for some soft water fish that have been in captivity for many generations.
GH is a measure of calcium and magnesium.
If you want it harder, you can add GH booster or Seachem Equilibrium or any similar product.
If you know your water does not have the right balance between these minerals each is available separately. For example, if you knew you needed magnesium, but were OK for calcium, then Epsom salt is a good source of magnesium. If you knew the calcium was low, but magnesium was OK, then calcium chloride is one possible calcium source.

KH of 7 is pretty good for any of the hard water critters listed above, yet is still soft enough for some of the fish that have been in captivity for several generations, even if their ancestors came from soft water.
KH is a measure of carbonates. To add more carbonates you can add bicarbonate of soda, aka baking soda. If you do not want to add sodium to the water then potassium bicarbonate is also available, I think it is sold for kitchen use, I have seen it for sale on line.

As far as I know the products you are listing have none of these materials, so should not raise GH or KH. Read the labels to be sure, though.

For soft water animals, GH and KH as low as 3 German degrees of hardness is just fine, though I would research the species you are interested in to be sure.

Doing a 50% water change with RO ought to cut the GH and KH almost in half. It is surprising they just about do not change with a 50% water change. That is really odd.
Have you tested the RO water? As the membrane ages it is less effective at removing things.

 

[Chiefston]

Thanks for the reply Diana.
I'm getting my RO water from the Water and Ice store down the street, and I'm pretty sure their setup is fine. I will double check the water I get from there next time though. I just recently changed from topping off my tank with our liquid rock water here in AZ, to topping off with RO water. I think that was part of my problem earlier, but not to the degree I'm currently experiencing.

 

[Diana]

If you are keeping hard water critters, then a balance between RO and liquid rock will be just fine for them.

If you are keeping fish or shrimp that need soft water you might end up with almost pure RO and let the rock add the low level of minerals they need.

Definitely test the RO. I have seen posts from other fish keepers who buy from machines outside grocery stores, and it seems those machines are not always serviced properly. You might need to get your own RO set up. There are small ones that are portable. The problem with RO is that the membrane does not handle certain minerals (Calcium, maybe magnesium) very well, so it is better for that sort of membrane to run the water through a sodium exchange water softener 1st, then use the RO to remove the sodium (which it can handle)