Looks like it doing what it's supposed to do. The foam is the fermatation process taking place.It should lessen some in the next few days. Hard to tell from the pic, is it jello mix or just water?
Do you have a smaller bottle between this one and your tank to count bubbles and catch any mixture that may go up the tube?
If it's just water, drain a bit out to prevent this. I normally only fill mine to about an inch below the shoulder of the bottle. this allows me to give it a good shake from time to time without having the mix flow up the tube.