Just a FYI. Temp and tank lids.

I recently removed my tank lid while cleaning and forgot to put it back on. I went to move a rock the next day and the water was cold...so I got pretty mad as my one fish died. I blamed the heater and don't have the money to replace it. So i set it up in the DT turned it on higher and monitored the temp every 30 minutes. It just hit me.. Nothing is wrong with the heater. The lid being off allows my rooms fan to cool the tank excessively. Here's a lesson learned the hard way.

 

I have screen tops on my tanks. Honestly having glass tops traps in gases and doesn't allow proper gas exchange. And you had to have some serious fan movement to cool the tank fast enough to cause harm to the fish IMO. Unless you keep your house at like 58

 

We keep it at 72. My fan is on 24/7. This was over 24 hours.

The edge of the fan blades are probably 6 inches away from the tank.

 

I have always had a full hood or glass cover on all my tanks, and I've never had any problems. As long as it's not air-tight and you have good surface circulation, gas exchange is not affected to any noticeable degree.

 

Maybe your heater is too small for your tank. My 60g is downstairs where at night it gets 65 degrees and my tank never gets below 77.

 

It's a 300 watt heater. 105 gallon total system.

 

6 feet away?

Sorry for the loss

 

From the picture it looks like a 30 gallon tank, not 105. I'd check the heater because I have no lid on my 36 bowfront and never have a temp problem.

 

Looks more like a55 to me. 4' long right? +1 to watching that heater, should still be able to keep up with that.

 

Been a while since I looked at wattage per gallon but 1 300w for a 100+ sounds like it's not enough. Assuming of course its that big.