Help... Heater boiled the sand bed

[JWGarber]

Ok long story short I am in the middle of breaking a tank down to move it.

Well I left the tank half full with both pumps running and all equipment etc.
I had slid my heater sideways in the tank to ensure it was submerged.

Its probably been 3 days by now but tonight I kept hearing a thumping noise from the tank. My girlfriend mentioned it last night and I thought she was hearing one my large hermits moving against the glass.

Turns out the heater had fell into the sand and was inserted into 3 inches and boiling the water/sand at the bottom.
It was thumping enough that the sand was bubbling up with each thump. So it was either the glass thumping or bubbles from boiling popping against the glass.

I pulled the heater out and sifted a bit of the sand to let water flow around it.

Its of course not thumping now but my questions is how much heat can a glass bottom tank handle.

It got pretty darn hot. I stuck my fingers down into the bottom and while it didn't burn me it was borderline uncomfortable.

Is this a time bomb waiting to happen or should it be ok? Rimmed tank should be a tempered bottom.

 

[JWGarber]

It stopped the thumping when I pulled the heater from the sand and so far seems ok. Its still quiet and has not made any thumping sounds since.

I mean it thumped enough that I could feel it in my hand and see the water tremble before I pulled the heater out of the sand.

I am just worried that it could give away... Are the bottoms of most aquariums heat safe?

 

[fishysteve]

Why didn't the heater shut off when it got to the set point?

 

[JWGarber]

I think because enough of the heater was still out of the sand that it didn't shut off.

Its a long 300w heater.

I am just a bit worried that the bottom is now weakened.... any input?

 

[JWGarber]

I plan Monday evening to pull the CUC out and put em in my 20l temporarily while I move the tank to its new location. Problem is now I am afraid of what will happen between now and monday and that this might have weakened the bottom. When I start adding all my live rock back in what will happen etc..

 

[JWGarber]

Double Post... weird..

 

[fishysteve]

I'd imagine the tank is fine. If the water was boiling, how can the cuc be ok?

 

[JWGarber]

The heater was only boiling the bottom of the tank right in the spot where the sand was covering it.

So about 3 inches of sand and it was popping and boiling underneath that spot of sand.

The rest of the tank average temperature was only 76f everyone in the tank is acting normally.

So just that specific spot of the bottom of the tank was being heated really high and the tank was popping and sand was actually bubbling up during each pop. It was not a rapid popping sound more like a heater vent sounds when it cools after heat turns off in a house. Popping and cracking.

expansion and contraction etc..

What scares me is was the glass popping or the water/sand popping as it heated.

 

[woodenhez]

I would think the glass is ok. Close call.

 

[JWGarber]

I'm still twitching about it....
Scared to sleep but I gotta work one more day before I am off and back working on the tank.

I cleared a lot of sand out of that area and while I cannot see the glass I ran my hand all around it. It doesn't feel like there are any distortions or cracks etc...

It seems ok but sheesh man... with it popping the way it was. I am still nervous.

I mean you could even see the sand pop up in the air with every thump and occasional bubbles escaping. That is how I figured it out. I noticed the heater was end first in the sand and every thump coincided with a bubble of sand coming up.

 

[syrinx]

I have seen heaters crack sumps- say of 30 gallon size or so. Usually it happens when the sump is drained, and the heater left on by mistake. The heater is water cooled- thus when there is no water flow around it- it overheats. As far as the tank goes- if it did not break, it is likely not effected. 212 degrees is not that hot in the world of glass. For example- tempered glass is taken to 720 degrees celsius. Tempered glass is also used for baking dishes and whatnot. As long as there are no cracks, and the silicone is undamaged- I would not give it a second thought.

 

[syrinx]

And just in the stream of conscience- wouldnt it be logical to assume if it were an extreme situation, that the thin heater glass would have broken before the tank?

 

[JWGarber]

Everything seems fine with the tank. It was just a very uncomfortable sight to see sand bubbling up from the heater.

Good point about the glass of the heater not breaking. I never thought of that.