Dish soap is a surfactant---removes oils. Not too much trouble in that department, except as it finds its way into sponge pores and coral pores, but some soaps are antimicrobial, a problem for the sandbed and rock. If it's of any comfort, dish soap is purer than laundry soap. When you're doing wild bird rescue or recovering fine needlework from fire damage, it is the preferred soap, because it will not bleach and is lower in phosphate. Much commercial soap is through the roof in phosphates---a problem in the tank, for algae growth.
If you have no ro/di head for your local supermarket, walmart, etc, that's got one of those kiosks. Let child go with you, to appreciate how much fuss this is.
Change water, change, and change, skim wet, and I'd run some phosgard, just on general principles, along with carbon.
