Look up your water company. Sometimes they have real time monitoring. I would guess the test kit is off with tap nitrates that high. The EPA legal limit is 10ppm which we hit here in Iowa and they had to install an expensive treatment facility and there are lawsuits over it all. Above 10 can get babies very sick and even die - so I would 1st suspect test kit error IF you are on city water. Well water is another game. I use RO/DI in my tanks here. Because cities have to be so conscious of liability if babies get sick almost always when people test their tap (city) and its above 10 it's test kit error. Not that it isn't possible.
https://safewater.zendesk.com/hc/en-us/sections/202346267
Edit: sorry I didn't see your location! The above is applicable to US only. My bad!
https://safewater.zendesk.com/hc/en-us/sections/202346267
Edit: sorry I didn't see your location! The above is applicable to US only. My bad!