This same advice goes for OP /u/TheNovaForce as well:
I had a similar issue. Get a PH tester like this one: https://smile.amazon.com/gp/product/B072JVRPFY/ and swish it around in the water for a good 30 seconds or so to get a reading. If the number is less than 7.0, you have acidic water which is eating through your copper pipes - anything below 6.5 is basically a "fix this ASAP" situation. You'll need to add an acid neutralizer (I used this one: https://www.midatlanticwater.net/shop/acid-neutralizers/non-backwashing-acid-neutralizers/acid-neutralizer-10x54-non-backwashing-wbypass ) and you'll want to get your pipes checked and possibly replaced if they have signs of pinhole leaks or corrosion.
If you don't have acidic water, then either a toilet cleaning tablet got stuck in your toilet somewhere (under the flap or in the throat of the toilet where the tank drains into the bowl, perhaps?), OR you have a bonding issue like /u/Waspy1 indicated and should have an electrician come take a look
Same experience here. I got mine for my kombucha, and it was just a random one off Amazon, around $20. It came with some calibration solution powder as well. It's been reliable since I got it last year.
Edit: this one, more like $15. https://www.amazon.com/VANTAKOOL-Accuracy-Measurement-Household-Drinking/dp/B0789G7MVP?keywords=PH+meter&qid=1537457868&sr=8-3&ref=mp_s_a_1_3
https://www.amazon.com/Pull-Together-Floating-Thermometer-Resistant/dp/B081RM21KX/
In all seriousness, if you want a better suggestion, you need to put some effort in here. What features do you want? How will you use the data? What do you have for existing smarthome infrastructure? Is there Wifi coverage at the pool?
Thanks for the response! It's this kit: https://www.amazon.co.uk/gp/product/B004UAFVEG/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1 so doesn't actually test for ammonia.
We do have a filter, but no idea how long they had it before or how old these fish are.
$14 on amazon, comes with kit to calibrate the gauge. Hasn't steered me wrong
VANTAKOOL Digital PH Meter, PH Meter 0.01 PH High Accuracy Water Quality Tester 0-14 PH Measurement Range Household Drinking, Pool Aquarium Water PH Tester Design ATC (Blue) (Yellow)
https://www.amazon.com/dp/B0789G7MVP/ref=cm_sw_r_cp_apa_i_ANE1BbM20SMKG
That's the one I use also, here's a link! Comes with a calibration kit
VANTAKOOL Digital PH Meter, PH Meter 0.01 PH High Accuracy Water Quality Tester 0-14 PH Measurement Range Household Drinking, Pool Aquarium Water PH Tester Design ATC (Blue) (Yellow)
https://www.amazon.com/dp/B0789G7MVP/ref=cm_sw_r_cp_apa_i_pW81BbJWJT61Z
PH calibration solutions: $13.69 https://www.amazon.com/General-Hydroponics-4-01-Calibration-Solution/dp/B017H73794/ref=redir_mobile_desktop?_encoding=UTF8&dpID=51Kpq0j-fmL&dpPl=1&keywords=general%20Hydroponics%207.0&pi=AC_SX236_SY340_QL65&qid=1517523500&r...
All you need. Mine has lasted 4 years with very little calibration needed. Test it using these 2 solutions at least before every grow.
There's some contention in the Aerogarden community about trimming roots. I personally don't and have no problem growing. A lot of people do though.
Going off your picture, it looks like your nutrient levels might be a bit too high. It might be the picture, but the water looks darker than it should be.
Leaf browning, unfortunately, can be caused by... well... most things, so it's hard to say what the issue is. I'd say, whether you want to pursue the root trimming or not, drain the water as much as you can, give it fresh water and fresh nutrients if you haven't done it recently.
I also recommend getting a cheap PPM/EC meter, something like this: https://smile.amazon.com/gp/product/B071LGTG7W/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1
or
http://www.aerogarden.com/accessories/tds-temperature-meter.html
Might not be necessary, but it's really cool and helps you hit the nutrient target easier.
I own a TDS meter for testing my RO/DI water I use for my saltwater fish tanks. For that I want the reading to be pretty accurate because anything more than 0 ppm means i have to replace my filters. For travelling the accuracy isn’t as much of a concern, being 1 or 2 ppm off when your reading is north of 400ppm won’t make a difference. For drinking water you want to just make sure that it is < 500 ppm (The EPA's rescommended maximum level of TDS in water is 500mg/L (500ppm)), personally in the US of A i won’t drink tap water that reads > 300ppm (My Moms tap water in Chula Vista, CA reads 425ppm). In mexico, all their water is > 300ppm.
The PPM reading might not save you from getting sick because it’s just mesuaring total amount of mobile charged ions, including minerals, salts or metals dissolved in a given volume of water but with readings that are way above normal you usually see higher concentration of bacteria which you don’t want to drink.
Anyway, that being said I have one of these for travel. They ship from Hong Kong so expect it to take about a month to receive it, if you buy one that is.