Malfunctioning Heaters

[rdd1952]

I thought I would throw this out in the scientific section to see what evidence is out there to answer the question. I'm terrible at researching the scientific side of things.

Having just read another thread about a faulty heater boiling the fish, I am wondering if the high water temperature (probably in the 90s but possibly over 100 I guess) resulting from a faulty heater is really the issue or is it more a matter of lack of oxygen that kills the fish as fish in tanks with high temps are always gasping at the surface.

 

[xx-miss-limber-xx]

If it was my thread you were refering to, id say (non-scientificly) it was the boiling temperatures that killed my fish, they litterally looked 'cooked' when I found them, and I was only out for a few hours so im not sure if the oxygen levels could have gotten 'that bad' seeing as the filer was on and the massive airstone i have running along the back of the tank (like a wall of bubbles)

But im not sciency lol... just tellin you what I came home to find lol. poor fishies didnt stand a chance, the water was too hott to have a bath in! x

 

[OohFeeshy]

Presumably it depends on the exact circumstances. A large tank will have a slower temperature increase, so probably it would be oxygen in that case. A smaller tank would increase more rapidly and probably to a higher temperature, so although I would still guess oxygen was the main factor 'boiling' would be quite a problem too.

 

[aaronnorth]

Are people inclined to agree with oohfeeshy then?

i found this which is quite interesting, however i am unsure if that is O2 alone, because if it is then other gasses will affect the saturation levels - plus our aquariums arent 100% saturated anyway,
http/kywater.org/ww/ramp/rmdo2.htm

 

[helterskelter]

It also depends on the fish, some fish are fine at high temps and low oxygen ie betta's....

Danio's prefer cooler water with more oxygen.

At around 30C with no aeration this is border line for most active fish, while the slower fish tend to go more.

 

[OohFeeshy]

I would *technically* say that 'boiling' occurs when the water gets to such a temperature as to denature the protein present in the fish; i.e. literally cook it. I haven't looked very well, but having a look at some sous vide articles, around 40C seems to be the very minimum temperature, and that only causes the muscle fibres to swell- cooking takes a very long time. Based on that, and thinking of it biology in general, it's going to be oxygen. The increased temperature also causes an increased metabolic rate, obviously increasing oxygen demand whilst the water steadily becomes less saturated with oxygen.

 

[Bignose]

plus our aquariums arent 100% saturated anyway,

If they aren't at 100%, they are pretty darn close. With all the water movement and the large surface area, the water is going to equilibrate very quickly and stay very close to equilibrium simply because we try our best to minimize rapid changes.