I am having the same issue but mine is from a bubble stone powered by a tetra whisper pump, it bubbles bad in my 55 Gallon tank but I have the same setup basically in a 10 gallon and it doesn't bubble up at all. It's making my head hurt trying to figure it out
Foaming just means there's something in the water. In an established tank it could just be dirty water or the use of something like Stresscoat. In a new tank it could just be mold release on the ornaments or something.