Soaps are typically amphipathic hydrocarbons, meaning they have a non-polar end (the hydrocarbon) and a polar end (phosphates or sulphates are common), and then they add in the stuff that makes it smell good and feel good on your skin and whatnot. These phosphates would probably bind to GFO, but are not available to the organisms in your tank, at least not in any appreciable rate, as their cellular machinery is not built to take up such phosphates like they are inorganic phosphate or more "natural" conjugated phosphates typically present in their environment. That said, I learned many years ago to never underestimate what bacteria will evolve to use as a food source, so take my previous statement with a grain of salt. Now, there is very likely unconjugated phosphates in such soaps as well just due to their manufacturing process, and these would absolutely be available to algae and whatnot. Testing the water for phosphates would be a good idea.
The good news is, skimmers are pretty much tailor made to pull compounds that look like soaps out. They are small, they are sticky, and they are charged, so they loooovvvee the surface of bubbles.
Here is what I would do in such a situation.
1) Run new carbon. This should help you pull out some of the detergent molecules and the "extras" that were in the soap
2) make sure my skimmer is allowed to do its work. Keep it clean, make sure your skimmer cup never gets a chance to fill up.
3) Run GFO. Best to not shock your system with a huge increase, but adding some could certain help pull out the phosphate-containing compounds.
4) Do a water change. As always, the solution to pollution is dilution. Water change should be a part of almost any water parameter malfunction.
5) Cross your fingers, and hope for the best :/. I really can't even hazard a guess as to what the effects will be. Good luck man!
