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I've got a 20 gallon planted tank with a sponge filter, sand substrate, and a Nicrew light. Running it for about 3 months now, but my Java Ferns are turning brown at the edges. Water params are good, 0 ammonia, 0 nitrite, 10 nitrate. Any ideas what's up?

Java Ferns can be picky about lighting. That Nicrew might be too intense for them. Try reducing the photoperiod to 6 hours or raising the light a bit. Also, check if they're buried in the sand, their rhizomes need to be exposed.

I agree with FinMaster. Too much light can cause browning. Are you using any fertilizers? Java Ferns are slow growers but still need some nutrients, especially if your tank is low on organics.

FinMaster wrote: ↑Fri Sep 12, 2025 5:32 pm Java Ferns can be picky about lighting. That Nicrew might be too intense for them. Try reducing the photoperiod to 6 hours or raising the light a bit. Also, check if they're buried in the sand, their rhizomes need to be exposed.

Yep, rhizome burial is a common mistake. If they're buried, unearth them and attach to driftwood or rocks instead.

What's your water hardness like? Java Ferns prefer softer water. If your GH is high, that could be stressing them out. Also, how often are you doing water changes?

Thanks for the tips, everyone. I'll try raising the light and checking the rhizomes. My GH is around 8 dGH, and I do weekly 20% water changes.

8 dGH should be fine for Java Ferns. Another thing to consider is flow. They don't like strong currents. If your sponge filter is creating too much turbulence, that could be an issue.