Had my swimming pool for like35 years. For most of that time I really have not done "major" shocks. What I do is chlorinate to maybe 6ppm or so and then let the chlorine get back town to 0. Varying chlorine content is the most efficient way to keep algae from growing (IMHO). Less chlorine is better..ask your liner. Anyway with the pandemic it became difficult to get liquid chlorine which is what I have mostly been using for the last several years. I ordered 50 lb of skimmer tabs on Amazon. They each weigh 7.2 OZ. What I do is break them up in their plastic wrappers and dissolve them. I use 4 tabs per "mini shock" and it lasts 5+ days. The tabs at $1 each so basically 5 bucks a week for chlorine and since they have stabilizer, its a pretty good way to go. My pool is 18 x 36 but the depth is 32 inches so thats like 17,500 gallons of water.