Water Quality Readings - Confusion!

Hello everyone,

I am very confused about water quality and how to understand what readings I should use.
My water supplier gives values of 215 mg/l CaCO3, 15 degrees clark, 13 degrees German.

I have just tested the aquarium water using the NT Labs Aquarium lab (all drop tests) and have gotten a KH of 5 and GH of 7. Plus I used a TDS meter that my partner had and it gave a reading of 165 ppm.

I know water values can change with standing, temperature etc. My tank has plant soil covered with black sand, plus bog wood and medium levels of live plants. I currently have 2 honey gouramis and 12 celestial pearl danios. They have been in for a total of two weeks, looking well, have settled and now used to seeing me so that’s good 

My aim is to find out what water levels to use when choosing fish?!
And is there a better way to accurately assess your water quality, something the pros rely on and has been proven time and again?

Thanks for all your help - I know this is a common topic but I could quite figure it out, despite scrolling through pages of queries!
 

Thank you @fcmf

So I testing some water that had been standing for 24h and some tap water....both came out pretty much exactly as the water company said. Then I looked up sand (100% inert) and soil...not so inert! I thought I had bought a “normal” brand but the soil is JBL proScape plant soil and, sure enough, in the information it states that it will make water slightly acidic (I expected this) as well as lower the KH and make the water slightly softer.

So thank you for giving me the tools to solve this! And I’ll put it down to noob errors   

  Now the question remains...
If it is the soil making the water softer, then should  I keep fish that prefer the actual water conditions of the tank? I think yes?
And considering the effect of the soil, will water changes from my tap water be shocking the fish?

Hi @jaypeecee

It’s a Hanna DiST 1 although it looks like an older one (I found it in my partner’s tools) so may not have been calibrated for a while. The 24 hour standing tap water came out at 213 and fresh tap water at 196 which gave me a bit of reassurance as the water company quote 215 mg/l CaCO3...I was assuming these are the same measurements but not sure what else TDS might measure besides the CaCO3...

What calculation are you thinking of? I’m definitely up for learning about what all these figures are and how they relate to each other, so I can go beyond simply knowing the “right” numbers.

Thanks for responding!

Now the question remains...
If it is the soil making the water softer, then should  I keep fish that prefer the actual water conditions of the tank? I think yes?
And considering the effect of the soil, will water changes from my tap water be shocking the fish?

Hi,

It is not difficult to adjust water KH and GH independently of each other. A KH of 5dH (German degrees hardness) will provide reasonable buffering against pH changes. A GH of 7dH is considered to be "slightly hard". Refer to https://www.seriouslyfish.com for choices of suitable fish.

JPC

@jaypeecee no worries! And thanks for the extra info. I’ve never had any fish before and I’m finding one of the most amazing things in fishkeeping is that it’s not all about the fish...it’s a whole new world of chemistry, botany, biology and more. So cool to be learning like this again! Thanks for your help   

Still a little concerned about the difference in the tap water and aquarium water for when I do water changes. Will this possibly shock the fish? I know temperature and pH do but will a big difference in hardness do the same?!

Hi,

Yes, it's exciting, isn't it? My background is rooted in science but not the life sciences. So I love making new discoveries about the science side of fishkeeping. There is a lot to learn but just go at a pace that suits you.

When doing water changes, it is possible to shock/stress the fish. And, of course, the bigger the water change, the greater the risk of this happening. A fish's osmoregulatory system balances electrolytes between that of the water with that in the fish's body. Examples of electrolytes are - sodium, calcium and magnesium. When conditions disturb the balance of electrolytes, the fish may be under stress. And this may result in an infection. In the first instance, a quick comparison (with an EC/TDS meter) of the tank and tap water is very helpful. Then, follow up with KH and GH measurements.

Could you please summarize the difference in EC/TDS, KH and GH measurements between tap and aquarium water that you are currently using?

JPC