Many people are unaware of how to properly care for their acrylic products. Even if you do not own an acrylic fish tank, chances are something in your tank is, protein skimmers, phosphate reactors, sumps, HOB refugiums, etc. I have compiled a list of info on how to properly care for your acrylic:

Cleaning

In order to keep acrylic as clear as the day you first got it, forget anything you knew about cleaning glass. Cleaners strike a slow dulling blow to acrylic every time they are used. Cleaners in this case, are any typical household cleaners such as WINDEX, 409 any anything with ammonia or abrasives. These products with each use cause millions of micro scratches which quite quickly lead to a cloudy appearing surface. The method of application is also crucial, as paper towels, newspaper (my personal favorite glass cleaner) and even dry soft cloths will scratch the surface.

So I am sure at this point you are terrified of even touching your acrylic, but no worries, it is extremely easy to clean. Take a Clean soft cloth, do not mix your cloth you wipe off salt creep with your cleaning cloth, and either apply a little water, or an appropriate acrylic cleaner which I will list below. The use of mild soap is also acceptable. Just remember to avoid heavy pressure on the surface, as it is not necessary and avoids the possibility of dirt within the cloth to scratch the surface.

Microfiber cloths are great for cleaning acrylic, most auto-parts stores carry them.

Cleaners

Novus makes a great line of acrylic polish and cleaning products that comes in 3 steps, step 3 for heavy scratches to step 1 as a final clean/anti static coating. Brillianize makes a great final clean product that I prefer slightly over Novus. I recommend getting one of the two, simply because these are "plastics" cleaners, not just acrylic. Take a look around your home, chances are there is plastic stuff everywhere from computer screens, TV's, clocks, etc.

For light scratches, Novus 2 and 3 work well. If you know how to wax a car, then these same techniques are used. Just remember to keep a separate cloth for each step, and a separate cloth for the final wiping.

For heavy scratches, a lower grit sandpaper must be used, depending on severity of it, around 400-800 grit. For external scratches, I personally like to take my sanding all the way up to 8,000 grit (that is not a typo), this allows less polishing and less chance of any deep scratches remaining. Once you have sanded the scratch flat, a soft buffing wheel is easiest on a drill with Novus 3 or polishing compound. However, with a lot of elbow grease, this can also be accomplished by hand. Follow up with Novus 2 by hand. For internal scratches on a running tank, a micro mesh kit is recommended. These kits can go up to 12,000 grit, and there is no polishing compounds involved. The key is to keep the surface wet and apply light pressure. Remember to keep that surface wet! Also, sand a larger area than the scratch, this will help to minimize any distortion that may occur.