@Pepere I personally have a five gallon plastic bucket I use that is over 30 yrs old. I don't know if you have a home depot or lowes in your area both sell durable buckets.
I have a set of 3 lens magnifying glass. The highest magnifying lens 20x. I can view something like for example a Cyclops very clearly. There are also magnifying phone apps.
@EggShappedFish I suggest sterilize aquariums with part bleach and water and rinse out. The traces of Chlorine from beach won't be a issue once dechlorinator is added to aquarium water.
@Stef I personally would replace the filter especially if it not running properly. If you decide to go with another Fluval AC 50 yes place a pre-filter on the intake. I would personally raise intake.