Can I fully submerge my heater?

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shapetrans
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Can I fully submerge my heater?

Post by shapetrans »

I just got a new heater for my 20 gallon tank and the instructions say it's submersible. But I've heard mixed things about fully submerging heaters. Is it safe to dunk the whole thing underwater, or should I keep part of it above the waterline?
flinty9
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Re: Can I fully submerge my heater?

Post by flinty9 »

Depends on the brand and model, mate. Most modern heaters are designed to be fully submersible, but some older or cheaper ones might not handle it well. What's the make and model? Also, check if it's got a waterline mark—some have a max submersion line.
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sand9e
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Re: Can I fully submerge my heater?

Post by sand9e »

I've got a Fluval M50 in my 30 gallon, and it's been fully submerged for months with no issues. Just make sure the cord isn't frayed or damaged before you dunk it.
Rivera
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Re: Can I fully submerge my heater?

Post by Rivera »

Yep, most heaters these days are built to handle full submersion. My Eheim Jager has been underwater for years, no prob. Just double-check the manual to be sure. If it's submersible, you're golden.
troutlet
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Re: Can I fully submerge my heater?

Post by troutlet »

flinty9 wrote: Mon Jun 23, 2025 11:02 pm Depends on the brand and model, mate. Most modern heaters are designed to be fully submersible, but some older or cheaper ones might not handle it well. What's the make and model? Also, check if it's got a waterline mark—some have a max submersion line.
Good point. OP, if it's a no-name brand, I'd be sketched out. Stick to reputable brands like Fluval or Eheim if you're gonna fully submerge.
marinero
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Joined: Tue May 07, 2024 9:30 am

Re: Can I fully submerge my heater?

Post by marinero »

I had a cheapo heater from PetCo once, and it shorted out when I tried to fully submerge it. Not worth the risk, dude. Spend a few extra bucks on something decent.
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fruitblast
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Re: Can I fully submerge my heater?

Post by fruitblast »

My heater's always been underwater, no biggie. Just don't let it touch the gravel or glass, or it might crack. Keep it suspended in the water column.
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shapetrans
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Re: Can I fully submerge my heater?

Post by shapetrans »

Thanks for the advice, everyone. It's an Aqueon Pro 100W, and the manual says it's submersible. I'll give it a shot and keep an eye on it for the first few days.
flinty9
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Re: Can I fully submerge my heater?

Post by flinty9 »

Aqueon Pro is solid, you're good to go. Just make sure the thermostat isn't buried in substrate or pressed against the glass, like fruitblast said. Heat distribution gets wonky if it's not free-floating.
Rivera
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Re: Can I fully submerge my heater?

Post by Rivera »

shapetrans wrote: Tue Jun 24, 2025 2:25 am Thanks for the advice, everyone. It's an Aqueon Pro 100W, and the manual says it's submersible. I'll give it a shot and keep an eye on it for the first few days.
Nice choice, that's a reliable heater. You'll be fine. Just don't unplug it while it's still hot—let it cool down first to avoid thermal shock.
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