Thousand Oaks, CA tap water
Supplied mostly by Calleguas Municipal Water Dist, plus 3 other utilities. Here's what the water means for your fish.
Disinfectant
Chloramine
Your water is treated with chloramine. Unlike chlorine, it doesn't gas off when water sits out, and many pitcher and fridge filters aren't rated to remove it. Conditioners that list chloramine on the label break it apart, which frees a little ammonia. Some utilities switch to plain chlorine for a few weeks a year.
Safety for fish and shrimp
Nitrite (NO₂)
Not detected (Low)
Not detected in testing, so any nitrite in your tank comes from the tank itself.
From California Water Board lab results (2023–2026).
Nitrate (NO₃)
Up to 2.2 ppm (Low)
Typically not detected
Not detected in testing, so water changes lower your tank's nitrate well.
From California Water Board lab results; Calleguas Municipal Water Dist, which supplies Cal American Water Co; Calleguas Municipal Water Dist, which supplies City of Thousand Oaks Water Department (2023–2026).
Copper at home taps
Up to 0.1 ppm (Low)
Typically not detected
Not detected in testing. Water that sits in household pipes overnight can still pick some up.
From California Water Board lab results (2023–2026).
Water chemistry
General hardness
161 ppm
Moderately hard. Great for livebearers, and most community fish adapt.
From California Water Board lab results; Calleguas Municipal Water Dist, which supplies Cal American Water Co; Calleguas Municipal Water Dist, which supplies City of Thousand Oaks Water Department; Calleguas Municipal Water Dist, which supplies California Water Service Co - Westlake (2023–2026).
Carbonate hardness (alkalinity)
120 ppm
Strong buffering. pH stays steady and hard to lower without RO water.
From California Water Board lab results; Calleguas Municipal Water Dist, which supplies Cal American Water Co; Calleguas Municipal Water Dist, which supplies City of Thousand Oaks Water Department; Calleguas Municipal Water Dist, which supplies California Water Service Co - Westlake (2023–2026).
pH
7.5–8.2
Typical 8.2
Alkaline. Many utilities raise pH to protect pipes. Stability matters more than the exact number.
From California Water Board lab results; Calleguas Municipal Water Dist, which supplies Cal American Water Co; Calleguas Municipal Water Dist, which supplies City of Thousand Oaks Water Department (2024–2026).
Total dissolved solids
420 ppm
A rough measure of everything dissolved in the water. RO water reads near 0, so TDS is a quick way to compare waters.
From California Water Board lab results; Calleguas Municipal Water Dist, which supplies Cal American Water Co; Calleguas Municipal Water Dist, which supplies City of Thousand Oaks Water Department; Calleguas Municipal Water Dist, which supplies California Water Service Co - Westlake (2023–2026).
Who supplies Thousand Oaks, CA
Calleguas Municipal Water Dist
Serves 50% of residents · Lake or river water · Chloramine
Cal American Water Co
Serves 23% of residents · Buys water from Calleguas Municipal Water Dist · Chloramine
City of Thousand Oaks Water Department
Serves 21% of residents · Buys water from Calleguas Municipal Water Dist · Chloramine
California Water Service Co - Westlake
Serves 6% of residents · Buys water from Calleguas Municipal Water Dist · 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.