White foam at the surface of the water?

Question

In the last few days my fish tank has had this weird white foam sitting at the surface of the water. The weird part is that it is only on the right side of the tank in the front and back corners. It is most foamy near the filter. My fish appear to be fine and I checked the parameters the other day and they are fine as well. What could this be? Thanks.

Answer 1

If you have male gouramis or betta, it's probably a bubble nest built by one.  If you also have a female, there may be eggs or fry in it.

Answer 2

It could be a bubble nest, or you could have added too much dechlorinating solution last time you did a water change.