Vet Q & AHow to clean hard water stains in a fish tank without harming fish?
If you are getting hard water deposits, use a utility razor and gently scrape the deposit off the glass. When you're doing a water change, if the water level drops below the deposits, use a cloth dampened with plain vinegar and scrub. Be careful to not allow any vinegar into the water. Wipe it well with a clean cloth to remove any vinegar residue and refill.
Ideally, the tank should be emptied, sprayed with vinegar, sit for 10-20 minutes then scrubbed or scraped.
Updated on September 24th, 2025