Who Gives A Fish Forums

My duckweed has been thinning out over the past few weeks. Tank is a 20 gallon, stocked with neon tetras and a few cherry shrimp. Water params are good, 0 ammonia, 0 nitrite, 10 nitrate. Lighting is on for 8 hours a day with a Nicrew Classic. No recent changes to the tank. Any ideas?

Could be the shrimp messing with it. Mine love to nibble on duckweed roots, kinda weird but they do it. Maybe try floating some in a breeder box to see if it grows better there.

Duckweed thins when nutrients are low, especially nitrates. Even if yours are at 10 ppm, it might not be enough. Try adding a liquid fertilizer like Thrive. Also, check if your light is strong enough, Nicrew Classics can be a bit weak for some plants.

berrymunch wrote: ↑Wed Aug 13, 2025 2:38 am Duckweed thins when nutrients are low, especially nitrates. Even if yours are at 10 ppm, it might not be enough. Try adding a liquid fertilizer like Thrive. Also, check if your light is strong enough, Nicrew Classics can be a bit weak for some plants.

Thanks, I'll grab some Thrive. Didn't think nitrates could be too low for duckweed.

Yep, duckweed's a hungry little thing. Mine goes nuts when I dose ferts. Also, if your water flow's too high, it might be getting pushed around too much. Duckweed likes it chill.

mudskip wrote: ↑Wed Aug 13, 2025 3:22 am Yep, duckweed's a hungry little thing. Mine goes nuts when I dose ferts. Also, if your water flow's too high, it might be getting pushed around too much. Duckweed likes it chill.

Exactly. High flow can stress it out. Try reducing filter output or moving the duckweed to a calmer spot.

Another thing, if you've got a lid, condensation can drip on the duckweed and mess with it. Not sure why but mine always does worse with a lid on.

That's a good point. Condensation can block light and create uneven moisture. If you're using a lid, try propping it open a bit or removing it for a few days to see if it helps.