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I'm setting up a 55 gallon planted tank and need advice on filter size. I've heard mixed opinions on whether to oversize or match the GPH to tank volume. What's your experience with larger filters in planted setups?

I've run a 75 gallon with a Fluval 407, which is technically oversized. The flow was a bit much for some plants, but the water clarity was insane. Maybe try adjustable flow filters?

Oversizing filters can work if you buffer the output. I use sponge pre-filters or point the spray bar at the glass to diffuse flow. My 40 breeder has a canister rated for 75 gallons, no issues.

graye wrote: ↑Sat Jun 21, 2025 10:18 pm Oversizing filters can work if you buffer the output. I use sponge pre-filters or point the spray bar at the glass to diffuse flow. My 40 breeder has a canister rated for 75 gallons, no issues.

Yep, diffusing is key. I've also seen folks use lily pipes to soften the flow in high-tech setups.

For planted tanks, I'd prioritize gentle flow over sheer volume. A filter rated for 55-75 gallons with adjustable flow would be ideal. Too much current can uproot delicate plants like Dwarf Hairgrass.

I've had luck with the Seachem Tidal series—they're HOB but have adjustable flow. My 55 gallon is heavily planted, and the Tidal 75 keeps things chill without blowing plants around.

Don't forget about media capacity. A larger filter means more room for bio media, which helps with stability. My FX4 on a 60 gallon is overkill flow-wise, but the extra media space is worth it.

If you're gonna oversize, just watch the surface agitation. Some plants like Amazon Swords hate too much surface movement. I learned that the hard way with a rippling surface and melted leaves.

The general rule is 4-5x tank volume turnover per hour for planted tanks. A 55 gallon would need 220-275 GPH. Anything beyond that risks disturbing substrate or plants.

I dunno much, but my buddy uses a small filter on his big tank and it's always cloudy. Maybe bigger is better?