KH question

[Phillip]

I have a small stock tank outside. I initially filled it with water from the hose. I haven’t topped it off with hose water anymore since the rain has been keeping it full. I sampled it today and noticed the kh is zero. I have some apistogramma sour there so the softer rain water should be good for them. 
 

Should I be worried about the low kh? Should I add something to help raise the kh? If I added something, is there something that won’t raise GH also?

Thanks!

[Mmiller2001]

I would measure GH, that's the measure of water hardness or softness. When we measure KH, we are measuring Karbonate hardness and this is often confused with water hardness. Not saying you don't know this, but just making sure! 

If you plan to only keep soft water fish, like Apistos, then 0dKH is no concern. I keep all my tanks at 0dKH and low or fluctuating pH is fine. 

I would focus my efforts at maintaining a stable GH, which is Ca and Mg kept in consistent ratios. You can use plain old Epson Salts for Mg and Ca can be bought very cheaply in the form of CaSo4. I would shoot for 3 to 5dGH.

If you do want to raise KH, keep no plants, you could use baking soda. However, it adds sodium and you will need to manage the sodium with water changes. If you keep plants, I'd use potassium carbonate. It adds potassium that will be utilized by your plants.

Hope this helps.

[Phillip]

On 5/25/2022 at 2:48 PM, Mmiller2001 said:

I would measure GH, that's the measure of water hardness or softness. When we measure KH, we are measuring Karbonate hardness and this is often confused with water hardness. Not saying you don't know this, but just making sure! 

If you plan to only keep soft water fish, like Apistos, then 0dKH is no concern. I keep all my tanks at 0dKH and low or fluctuating pH is fine. 

I would focus my efforts at maintaining a stable GH, which is Ca and Mg kept in consistent ratios. You can use plain old Epson Salts for Mg and Ca can be bought very cheaply in the form of CaSo4. I would shoot for 3 to 5dGH.

If you do want to raise KH, keep no plants, you could use baking soda. However, it adds sodium and you will need to manage the sodium with water changes. If you keep plants, I'd use potassium carbonate. It adds potassium that will be utilized by your plants.

Hope this helps.

Thanks for the detailed post! I guess my main concern was no KH causing pH swings. I guess if only rain water is used that shouldn’t be an issue? Also, the GH is still right around my what my tap water is 220. That needs to come down to make the apistos happy right? I’d assume that would come down with the addition of rain water?? 
 

[Mmiller2001]

Bringing it down would be ideal but they can live in it. I prefer to mimic their natural environment as best I can. Just monitor the GH and make sure it doesn't drop too fast. It will drop as it rains. A 2dGH drop in one day will stress them. I keep KH and GH changes to no more than 1.5 degrees in 24 hours.

[Phillip]

On 5/25/2022 at 3:26 PM, Mmiller2001 said:

Bringing it down would be ideal but they can live in it. I prefer to mimic their natural environment as best I can. Just monitor the GH and make sure it doesn't drop too fast. It will drop as it rains. A 2dGH drop in one day will stress them. I keep KH and GH changes to no more than 1.5 degrees in 24 hours.

Gotcha. Thanks!

[tolstoy21]

On 5/25/2022 at 4:09 PM, Phillip said:

Thanks for the detailed post! I guess my main concern was no KH causing pH swings. I guess if only rain water is used that shouldn’t be an issue? Also, the GH is still right around my what my tap water is 220. That needs to come down to make the apistos happy right? I’d assume that would come down with the addition of rain water?? 

Water params for apistos can also depend on whether or not they have been tank bred for generations or are wild caught, and which species.  Many tank bred species are tolerant to a wide range of Kh/Gh. Either way, a low Kh is ideal for them. I also keep mine at close to 0dKh.  If the water is evaporating and not overflowing out of the tub, then much of the Gh should remain in the water unless there are plants etc to utilize some of it over time. I don't think you need to do anything drastic if it lowers, maybe squirt some hose water in every once in a while to keep some Gh in the water (unless your hose water has a ton of Kh). I believe some species exist in the wild in water with close to no mineral content at all. I think rain water with leaves and twigs in it is the way to go.

Edited May 26, 2022 by tolstoy21