Mercedes, TX tap water
Supplied mostly by City of Mercedes, plus 1 other utility. Here's what the water means for your fish.
Disinfectant
Chlorine or chloramine
Utilities here use chlorine or chloramine, depending on which one serves your address. Chlorine slowly gases off from standing water; chloramine doesn't.
Safety for fish and shrimp
Ammonia (with conditioner)
Estimate0.15–1.36 ppm (Worth knowing)
Typical 0.77 ppm
This is what a conditioner frees when it breaks the chloramine apart. A cycled filter clears it within a day; a big water change in a new or very small tank adds more of it at once. Some conditioners also bind ammonia for a day or so.
Estimated from the chloramine level North Alamo WSC reports (2025).
Nitrite (NO₂)
Up to 0.1 ppm (Low)
Typically not detected
Not detected in testing, so any nitrite in your tank comes from the tank itself.
From EPA monitoring data (2012–2019).
Nitrate (NO₃)
Up to 4.7 ppm (Low)
Typical 0.8 ppm
Low, so water changes lower your tank's nitrate well.
From EPA monitoring data (2012–2019).
Copper at home taps (first draw)
Up to 1.42 ppm (Worth knowing)
The 90th percentile of first-draw samples from homes: water that sat in household pipes for at least six hours.
Shrimp and snails are sensitive to copper. Water that sits in household pipes picks up the most; it drops once the tap has run for a minute.
Published by your utility: North Alamo WSC's 2025 water quality report.
Chlorine or chloramine at the tap
0.6–5.6 ppm
Typical 3.2 ppm
At tap levels, chlorine and chloramine are toxic to fish, shrimp and the bacteria in a filter. Water conditioners are made for this range.
Published by your utility: North Alamo WSC's 2025 water quality report.
Water chemistry
General hardness
Not published yet
We haven't found this number yet. A drop test kit gives you your exact reading.
Carbonate hardness (alkalinity)
20–106 ppm
Typical 101 ppm
Moderate buffering. pH should stay fairly steady.
From EPA monitoring data (2012–2019).
pH
Not published yet
We haven't found this number yet. A drop test kit gives you your exact reading.
Who supplies Mercedes, TX
City of Mercedes
Serves 80% of residents · Lake or river water · Chlorine
- 2025 water quality report
North Alamo WSC
Serves 13% of residents · Lake or river water · Chloramine
Our data comes from public records and is still incomplete. Many utilities don't publish every number, so we're adding more all the time. Your city's range is a starting point: testing your own tap is the only way to know exactly what's in it.
Tap water lookup covers US cities only for now. Want to know why it matters? Read our story on tap water.
Compiled by Shoal & Stem from public records. Free to cite with a link.