What turns silicone yellow?

I recently applied some Silicone I to the outside of a pump, so it wouldn't hum against the glass in the sump. After just a few weeks, the silicone had turned a mustardy-yellow color. But it was out of sight/out of mind, so I didn't think much about it.

But now, the silicone in my new 10g hospital tank has begun turning yellow up at the top front corners. So, I'm starting to get curious.

Anyone know what causes this? I'd hate to have it happen in the DT; it's pretty ugly.

 

both instances is it silicone that you are applying? if so what kind?

 

No, strangely, it's not. The first instance is "Silicone I" that I applied; the second is factory silicone in the 10 gallon.

 

This is the pump I gooped the SiliconeI onto:

 

wow you werent lying about it being Mustard yellow... well this has got me.. the kicker is that its happening to factory tank silicone.

my tanks silicone is black so i dont think i would notice.

 

If it's your hospital tank, then it's probably something you dosed a fish with. When my fish got ich I remember reading on the back of the box that it can stain the silicone. My hospital didn't change, but maybe those different silicone you used were more prone to the meds.

If thats the case, then no worries about the display tank!

-amanda

 

The silicone near the light in my sump turns yellow also. I also used GE Silicone I as well. I dont really see an issues with it

 

so does mine... im interested in this

 

Well, other than the salt I use (Oceanic) there really is no common denominator between the two tanks where I've had this occur - so I'm stumped.

Let's see:

-nothing dosed in DT whatsoever, and only formalin in hospital
-totally different lighting
-different silicones

I'm beginning to think the cause might actually be biological.

 

both of these are definitely possibilities and what i think happened