Who Gives A Fish Forums

My guppies keep dying within a few months, even though the water params seem fine. I have a 20-gallon tank with a sponge filter, temp at 78°F, and do weekly 25% water changes. Any ideas what's going wrong?

What's your feeding routine like? Overfeeding can mess with water quality even if params look good. Also, are they getting enough variety in their diet? Mine thrive on flakes, frozen brine shrimp, and occasional veggies.

I had the same issue until I switched to a better heater. Cheap ones can have temp swings that stress guppies. What brand are you using?

jasmy wrote: ↑Sat May 17, 2025 2:32 pm I had the same issue until I switched to a better heater. Cheap ones can have temp swings that stress guppies. What brand are you using?

Yep, temp stability is huge. I run two heaters in my 30-gallon just to be safe. Also, check for aggression—male guppies can be relentless with each other.

Guppies are tough but finicky. If your tank's cycled and params are solid, it might just be bad genetics. Some breeders prioritize color over hardiness. Where'd you get yours?

Test for nitrates. Even low levels can shorten lifespans long-term. My guppies started lasting way longer after I added more live plants and cut nitrate to under 10ppm.

Thanks for the tips, everyone. I'll test nitrates again and look into a better heater. Appreciate the help!

Don't sleep on water conditioner either. Some tap water has chloramines that basic dechlorinators won't handle. Seachem Prime's my go-to.

How old are they when they die? If they're hitting 6–8 months, it might just be their natural lifespan. Fancy guppies don't always live long.

Mine bounced back when I added aquarium salt. Just a half teaspoon per gallon, but it made a difference. Could be worth a shot.