Need some advice - Black Silicone Turning Yellow

[Tetsuro999]

Hi Everyone,

I'm hoping someone can help me out with a possible problem I'm having with my aquarium. I've been searching through the forums looking for someone else with this issue but so far haven't come across it. Any help would be greatly appreciated.

I purchased a used 75 gallon aquarium three years ago but I believe the tank is around 5-6 years old. The person I bought it from said it still has the same silicone it was originally sold with. The silicone was completely black when I bought the tank and stayed black until the past 5-6 months when it started turning yellow along the inside bottom of the tank and about 3 inches up the side from the bottom. Some parts of the silicone are almost clear now. I haven't noticed any of the fish picking at it and it doesn't seem to be lifting but I'm still concerned.

Is it possible that my substrate could be changing the color? I have a thick layer of white silica sand, which has been in the tank for the past two years, and layer of black sand purchased at a local pet store, which was added over the past year. The reason I question the sand causing issues is that only the silicone touched by the sand is changing colors. The rest is still black. However, I use the same combination of substrate in another tank with clear silicone and haven't noticed any issues.

I keep an Oscar, Pleco, and a Convict in the tank.

I'm wondering if this is just something that happens to black silicone over time or if I should be really worried about leaks or the tank bursting. It's in a room near a lot of electronics that could be easily ruined. I've been considering purchasing a new tank just so I don't have to worry about it but if it's not cause for concern I could definitely use the money elsewhere.

Again, any ideas would really be appreciated.

Thanks,

David