I Lost My 40-Gallon at Christmas

I could see the tank from the front door. The waterline was too low. My gut sank.

Then I felt it—warm, damp air. I dropped my bags and ran.

The heater had failed. I don’t know exactly when. Sometime after I left for my parents’ house, it stopped regulating and just kept heating. The water was over 90 degrees. Everything was dead.

I lost two female bettas I’d had for two years—a koi and a platinum. Six otocinclus. A rescue guppy. A nerite snail.

What I felt

Guilt, mostly. I built that tank. I was supposed to take care of those fish, and I didn’t.

Equipment fails. I checked everything before we left—it all looked fine. We were only gone a few days. But knowing that doesn’t help when you’re staring at a tank full of dead fish.

I’m still processing it.

What I didn’t know

I bought the Hygger heater because it had overheating protection. Digital controller, automatic shutoff at 94°F. I thought that was enough, but it wasn’t.

The built-in thermostat failed. With nothing else monitoring the temperature, it just kept running.

I didn’t know external temperature controllers existed. I wish I’d known that before.

What’s next

I needed to understand what happened. Not just “the heater failed” but why a heater with a built-in thermostat could cook a tank.

I spent hours reading. Forum posts, product reviews, Reddit threads. Thermostats can stick, fail mechanically, or lose calibration. When they do, the heating element keeps running with nothing to stop it.

That’s when I found external temperature controllers. They monitor water temp independently and cut power if something goes wrong.

Inkbird ITC-308S. It’s made for aquariums.

I ordered it and installed it on my 110-gallon the day it arrived. Every tank I run from now on will have one.

Before I rebuild, I’m running a 24-hour leak test. Heat can compromise the silicone seals.

The 40-gallon is getting rebuilt, but not as a fish tank. I’m building a paludarium—half water, half land. Tiered structure with eggcrate and PVC. Lagoon-style aquascape at the bottom with shrimp and inverts. Vivid emersed plants growing out of the top.

I’ve never built one before. I’m reading, watching build videos, planning the structure. Learning how people do this right. External temp controller from day one.

I’ll document the build—what works, what doesn’t, the adjustments along the way. Maybe it helps someone else. Or maybe I just need to write this down.

The tank will run again. I’ll share what I learn.