Brand New Caldera Hawaiian spa, after 4 weeks of use th ewater has turned greenish. Ph, Alkalinity, chlorine levels ok as well as hardness. Shocking once a week. Any theories as to the green stuff?

Cleaned and degreased the filter for the first time, thinking that might solve the problem. After re-inserting it generated a lot of foam. Does that mean that I did not get all the filter cleaner residue off? Is this dangerous??

Best to bring water to your hot tub dealer or nearest spa/pool store for analysis.
Green water- well water with copper in it, or low pH water taking copper from the pipes in your house?

Dangerous- no. Try to really rinse those filters good, filter cleaner will foam. More annoying than anything.