Losing my mind with algae- Is it the new sand filter

I have a 18000 gallons gunite pool. I have been maintaining it for 6 years. Until this year no problems. I switched from a cartridge to sand filter because I was tired of cleaning cartridges. You can buy a sand filter for a little more than the cost of filters, so I said what the heck.

I previously had a Jacuzzi 330 sq ft tri clops cartridge. I bought a 300 pound Hayward S244T2 sand filter. We have a one horse power Jacuzzi motor. I installed and and the water looked great. Then I went on vacation with the grandkids and let me son in law take care of pool. 4 days in and I start getting cryptic text messages that the pool does not seem to be up to my standards. Of course he let chlorine drop.

I come back and brush it and shock it good (4 pounds of calcium hypocholorite ,and get pool looking great. Two or three days later I see algae on walls. Shock and brush again and looks OK for a few days and back to cloudiness and algae growing. Gone through this several times now. I think numbers are ok. The free chlorine levels are 7.5 -15 since I have been back from vacation. Ph 7.8, Alkalinity 80-90, CYA 55-65.

Here's my questions. I never had to brush daily or every other day with a cartridge filter. Seems every day now there a coating of algae on walls and floor. Before I would brush once or twice a week, maybe every two weeks. Is brushing more needed with a sand filter to control algae, especially on a porous gunite pool.

Do sand filters do a poorer job on algae? I am wondering if algae can get trapped in the sand filter and then just reseed the pool with algae once the chlorine levels drop a little. (I know cartridges can get real green, but you can clean them off and visibly see you got rid of all the algae. I am not sure if the algae's really removed from sand). Does algae get through a sand filter.

In any event the cartridge filter never seemed to cause this issue and I'm considering going back to it. I know in Ohio, this years been bad for algae because of weather I believe. I had algae blooms before with cartridge, but once the pool was shocked the problem went away. I am now spending more time with the pool when I thought I would just have to turn a backwash handle instead of cleaning filters. What do you folks think. Is algae more of a problem with a sand filter.