So confused by changes in KH

[PineSong]

My new co-op test strips show my KH as only 40, in both my main tank almost no water changes) and the QT tank daily water changes 25% and in a jug of Primed tapwater that is @ 12 hours old.

This is puzzling to me because I'm used to API strips saying my KH is high--my memory says it was usually 180 and the only photo I found showed at least 120 if not 180. 

I guess I'll have to buy another set of API strips and compare them side by side to know for sure, but if it is really only KH 40, should I do anything to change it?

Then.....

I tried to look at the city water quality report for answers, but it doesn't list KH in any form I recognize.

And to add to my confusion, its values for GH seem at odds with everything I know about my water. I live in a limestone region with hard water as identifiably by looking at glasses, coffee pots, fish tank water lines, etc. My GH has always been the highest color on API and on Co-Op test strips, but according to the city report GH in ppm (as CaCO3) averages only 128. According to another site (that sells water softeners!), my city averages 218ppm.

 

Basically I want to know if my water dangerously low in KH, whether it is hard enough for livebearers to breed and whether it has enough calcium in it for my mystery snail. Per the city water report calcium is 46ppm.

Any explanations/feedback welcome. 

And in case it matters, the rest of my parameters are:

Nitrate: 10

Nitrite: 0

pH: 7.2

 

 

 

 

 

 

[Littlefish]

KH 40 should be fine for livebearers.  I've run several planted tanks at kH 6.  

[Isaac M]

Hello @PineSong, a kH of 40ppm is rather low as that is about a kH of 2 dkH. It is rather odd to me that your aquarium that gets no water changes has the same kH of the new water. Unless those no water change aquariums have very low stocking levels and are decently planted, usually the nitrogen cycle over time will lower the kH and acidify the water (lower the pH). 

Water can also change seasonally. The city water report could also be taking an average of multiple sources. Water chemistry can even change between the treatment plant and your house. 

As far as the livebearers go, the kH of the water is the buffering capacity. The gH of the water is the hardness. Given that your gH is high, I would say your water is certainly hard enough for livebearers. 

I am not too well versed with calcium levels in a freshwater aquarium. But generally speaking, if it is only one mystery snail, I think it would be fine especially if you fed it calcium enriched foods. There are many snail and invertebrate based foods (crabs, shrimps, etc) that are calcium enriched. 

If you do find that your kH is actually that low, I would recommend some crushed coral to keep the pH from dropping as livebearers tend to like a higher pH (above 7). 

[PineSong]

On 8/13/2021 at 11:40 PM, Isaac M said:

Hello @PineSong, a kH of 40ppm is rather low as that is about a kH of 2 dkH. It is rather odd to me that your aquarium that gets no water changes has the same kH of the new water. Unless those no water change aquariums have very low stocking levels and are decently planted, usually the nitrogen cycle over time will lower the kH and acidify the water (lower the pH). 

 

Thank you, Isaac. Yes, my main community tank with (almost) no water changes is a 20g with only 3 otos, 3 Endlers, 2 guppies and 2 platies and a betta in it, and it has 10+ planted plants, some floating plants and until last week it had a boatload of pothos and other houseplants stuck in it. So that might explain the fact that it reads similar to the bare bottomed, floating plants-only QT tank which is a 10g with 3 mollies, 5 white clouds and 3 platies.

I do feed Hikari algae wafers for my snail.  

I will stock up on some crushed coral. The Co-op article on pH, GH and KH says to use a pound per 10g of water. I've never used it before so IDK what it looks like or how dense/heavy it is, but a pound sounds like a lot--before I read that article I was picturing a mesh filter bag full of crushed coral stuck in the HOB or something--a pound sounds like it will have to go somewhere else and will take up a lot of space.

 

[Isaac M]

@PineSong I believe the recommendation for a pound for 10 gallons is when you are using it mixed in with your substrate. When you put it in a hob, I believe you can use a lot less as it will dissolve faster being in a higher flow area. I would definitely make sure your kH is actually 40ppm before adding this to your aquarium though.

If your aquariums are doing well and testing well (fish and snail doing well, pH is not dropping/ kH is not dropping), I do not see why you would need to add anything to it. 

This is good information to know however if your aquarium begins experiencing a dropping kH/ pH. You can also read up on “old tank syndrome” to learn more about this sort of thing.