Dish soap Aka fairy liquid

Hi guys,

First off hi.

I'm a new user (long term lurker and reader) thank you for making your knowledge available as it has helped me in a few situations.
As per the forum rules.... I run a small pool servicing company in the UK with about 40 clients and have done for the last 6years.

My problem:
One of my clients has a 120m3 or 120000 ltr fibreglass pool next to field. I took the pool on this August it had gone green and was very very cloudy.
It is suffering from what I think is mustard/yellow algae. The client doesn't want downtime so I wasn't able to hit it too hard with liquid chlorine for the fear it would be down for more than a week.
So I have a return of the yellow sheeting and have discussed nursing the pool for the next couple of weeks until it's winter close.

One of the kids at the pool has poured 1ltr of dish soap over the slide which has gone in the pool
I can't find many posts on dish soap in pools. One place suggested that it may ruin the sand in the filter.... Why?
The return of the yellow sheeting algae seemed to happen after this soap went in the pool! I brushed the pool walls the week before.... So it may have been an unhappy coincidence!

Any thoughts or experience on the dish soap?
Or indeed just nursing the pool until it's close?
Chl 4.5 ph 7.4 alk 120 cyn50 copper 1ppm tds850 calc 150
Runs on a chlorine float takes 7x 200g multifunctional chlorine tabs a week to maintain the chlorine level at around 4.5ppm

I adjusted the ph to 7.2 and then hit it with 25ltrs of 14/15% sodium hyp on Friday afternoon closed it for swimming for the weekend. Plan to go in today and vac to waste, backwash the sand filter. Etc.

Many thanks
Stu