You are on the right track, and definitely need to shock the pool. You do need to get your Cl up to 20 ppm, and in a 25K gallon pool, 2 gallons should add 5 ppm. You're going to need to get it up to the 20 and hold it there by testing and adding more bleach as needed to maintain the 20 ppm until you are no longer losing chlorine when testing at night and again in the morning.

Along with shocking the water, you also must have good filtration. What type of filter are you using, are you running it 24/7, and do you see your pressure rising? What size pump do you have? Do you see any particles returning into the pool from the filter?

With 3 years' worth of using trichlor pucks, it's entirely possible that your CYA level was very high at the end of last season, and that it biodegraded into ammonia over the winter. This will cause an incredibly high chlorine demand, and may be what you're fighting. Unfortunately, the only way to overcome it is to keep at it with the chlorine until all the ammonia is gone. This can take lots of time, lots of bleach, and tons of POPP--pool owner patience and persistence. Unfortunately, trichlor pucks can make pool care easier, but only when you understand what it does to your water.

A question I have for you is whether your fill water is high in calcium or if you've been using cal-hypo at some point....high calcium levels can also cause pool clouding. Unfortunately, there's no way to know what's causing your cloudiness except to rule out one thing at a time....but with a CYA of 50, any chlorine level under 5 ppm is an invitation for algae, and yours is way under that.

By the way, welcome to the forum!!

Janet