I have never heard of a pump sock but it seems pretty descriptive. I can imagine problems but the idea of preventing mangled fish and damaged pumps is hardly new. That is a major reason for pre-filters that are attached to the intake. I wouldn't run a pump without one.

I can't be specific without knowing details of your pump. I can describe what I have. My pump pushes almost 6,000 gallons an hour. The inlet is 1.5 inches in diameter. I attached 6 feet of tubing to the inlet pipe. To the end of that tubing I attached a well filter. I had to use a couple of plumbing stepdowns to get the attachment size right. The well filter is a cylinder 15 inches long by 4 inches wide. It is perforated to allow free flow of water while preventing anything of much size to enter. I have used it with very few problems for eleven years.

There are many designs and materials for different situations. Many pumps come with a chunk of sponge type material which is a prefilter. I don't like that except for very small applications. The cage that holds the foam sponge makes a better prefilter except it doesn't catch particulates like the sponge does.

Thanks sleepless, I find your advice always sound. My pump is only 650 gph. I used to use the sponge filter, but find it a real hassle to keep hauling it out to clean. So I'm trying to find other options.

you can get a plant strainer basket,put the pump in the basket, and fill it full of the real lava rock.

I use a gallon paint filter in my catchment tank; it fits over the pipe, and I clean it once a month--you may need to clean more often.

The filter is a nylon or polyester fine mesh bag, got it at Ace Hardware.

Thanks for these interesting ideas. I'm going to explore my local Ace hardware store.

I forgot to mention; a giant hose clamp keeps the paint filter on the pipe

Dancing,
My pump is small like yours.
You just need a prefilter. They sell them for almost any pump that they sell.
Do you know what kind or brand of pump you have?
If you can find the paperwork that came with your pump, you can look it up online and buy them.
They aren't expensive.
They literally are made for your pump, and "clip" on to the end of where your water enters the pump.
They are also really easy to clean.
Look up prefilter on any Pond supply online.
They have to have your prefilter for your pump.
You usually get 2 for 9.99.

Thanks butterfly4u. I took your advice and bought a prefilter at the garden store. It's black and barely visible.

Another option suggested by the helpful staff at my local Ace hardware is a lint snare made for washing machine hoses, sold in packages of 2 for $2.99. I haven't tried that yet, thought, and would be interested if anyone else tries them.