Goldfish Pooping Blue

[LookingToLearn]

I have noticed that my goldfish are pooping blue. Is this normal? A week or so back I had some major issues with the nasty blue gravel I have in the tank, do you think the dust from that gravel could be the cause? Is this something I should worry about?
They are being fed TetraFin goldfish flakes iwth the occasional small slice of lettuce.
Thank you for any help.

 

[backtotropical]

I've never heard of that, LookingToLearn.

What issues did you have with the gravel, sounds like it could be related?