Believe me, no one can have asked (or thought of) more questions than I. hahaha BTW... no questions are dumb!

A pre-filter is to prevent plants, fish, etc from being sucked into the pump. It also helps filter out debris in the water that wouldn't hurt the pump but that affects the quality of the water.

Many pumps come with a pre-filter. I have a Pondmaster pump. The pre-filter came with it. It works great.

If a pump does not have a pre-filter, it is a good idea to make one yourself. This can prolong the life of the pump.

Anne

To add to what Anne has said, I guess a pre-filter is any filter element that is installed before the pump can pump water.

My pre-filter is in my Savio skimmer box. Water enters thru the leaf basket element, goes thru a side chamber x 2, and enters the back of the skimmer box where there is a poly mesh wall (the pre-filter). Water goes thru the mesh and into the larger area where the pump then discharges it.

I rinse it as often as possible, every day if I can!

Thanks, guys/gals. I notice that my pump has a built-in "cage" as a part of it, but since it doesn't seem to come apart, I guess it's not meant as a pre-filter.

I guess I have to make a pre-filter out of a plastic box that it would fit in, making the holes and putting the scrubbies in it, too, right?

And when you say it's meant to keep fish out, what about the baby fish? Our baby mosquito fish are teeny.

The filter/pump container described in the OP is one of many versions of what is called an Adam's filter. It is adequate for a small pond, 100 gallons or less. There are so many versions it makes it memorable to name it after a 12 year old boy.
Things that don't seem to come apart on a pump are usually just difficult to remove, especially if you have small hands. Try pinching any depression on the cover and twisting it counter-clock-wise at the same time. It takes a bit of doing the first time. The cage is a type of pre-filter designed to stop larger debris from getting to the impeller which is kind of like the big wings on a helicopter. The impeller should rotate freely. You need to access the impeller because things can wrap around the stem and slow it down or stop it. That can burn out the motor. Usually pumps come with a sponge filter between the cage and impeller. It is supposed to clean up smaller stuff before it gets to the impeller. Just about every one removes this sponge because it needs such frequent cleaning. Some other type of filter is used instead that is easier to access.
Remember, there is no one single way to put your system together but there are a few things to remember. Don't use short fibers such as that for stuffing pillows. The long fibers in quilt batting don't come apart easily so they won't wrap around the impeller. Check the impeller when you clean the filter. Lava rock is ok as a bio filter material but it clogs quickly and is very difficult to clean and it is very heavy. Scrubbies are one suggested bio material but there are many others. Sponge makes a pretty fair mechanical filter material but isn't as good as a bio material. It requires frequent cleaning. Any sort of pre-filter is primarily a mechanical filter but can be a bio filter as well. I hope I haven't confused you. Sandy

Here is a link that might be useful: Adam's filter

OK, I took your advice and took my pump's "cage" apart. Cool, I don't need to make anything else. I will get scrubbies to stuff into it. Thanks so much for what you wrote. (Oh, and I got a couple of guys for the brute strength part?? Didn't need them, as they pointed out the hidden 6 screws, LOL!)

I would not stuff scrubbies between the cage and impeller.
They may get sucked in. Also, it may cause your pump to overheat.

What should I put into it then, if anything? Thanks for this warning.

LOL! lsst is right. The reason they use the spongy foam insert is it has a fairly rigid shape that won't get sucked into the impeller unless it has been subjected to lots of wear and tear that softens it up, a lot. Just goes to show different people think differently. I'll give some examples of what I have done from time to time.
I use a rigid well head pre-filter that attaches to the intake of the pump with 3 or four feet of 1 1/2 inch flexible tubing. The water is pushed through 8 feet of 1 1/2 inch flexible tubing to a 100 gallon Skippy Filter which contains lots of scrubbies, old torn up netting and some other odds and ends for bio activity, a container of Activated Charcoal for tannins and in another layer, quilt batting for a final polishing of the water. The water leaves the Skippy through a 4 inch pipe that feeds a waterfall. Some people use a catch basket in a skimmer as a pre-filter. My next pond will have a skimmer but the Skippy stays. I want the skimmer because there are lots of twigs and acorns that work their way into my pond.
A smaller pond I built had a pre-filter that was a series of perforated boxes that each contained a foam filter that acted like a bio filter and a mechanical filter. Water passed through the filter boxes and through the intake, then out to a fountain. At other times the water went to a tank that had a rock settlement chamber before it went over a waterfall. The rocks worked but it was a pain to clean even if it was only once a season, so I switched to quilt batting. The boxes of the main pre-filter had to be cleaned weekly which was too much like work. I used the same boxy filters for a smaller pump that fed a small Laguna UV light. That worked very well since it was not the main filtering system. The box filters attached to the intake with a foot of tubing and the output took 2 1/2 feet of tubing to get to the UV box that sat on the side of the pond. there was a small filter pad inside the UV box to catch dead algae. That was probably more filter than needed but the fish loved the super clean water coming out of the UV.
As you can see there are many combinations that work. The idea of the pre-filter is to protect the impeller.
Some people attach hoses directly to filter and pumps, etc. with hose clamps. I have physical problems that make it difficult to stretch to loosen those hose clamps so I add those handy dandy screw on and off adapters for PVC.They still require hose clamps but I don't need to use a screwdriver to retrieve a filter or pump. Sandy

Here is a link that might be useful: Laguna bio/mechanical filter box

Sleepless, I am so NOT understanding this. The Laguna, is it its own bio-filter for inside the pond? Or do you put the pump inside it?

Now I am LOST as what I should do for a pre-filter for mine.

Anyone have any ideas? My hy-drive pump (4800) has its own cage. Do I leave it empty, or put something in it? I will have a Savio biofilter.

Do I put some kind of pre-filter AROUND the whole thing, cage and all???

I'm sorry I confused you. Be patient and I will try to do better. Did you look at the link in my last message? It shows a picture of the box filter I mentioned. It sits under water and would replace the cage on your pump. It is both a bio filter and a mechanical filter. I was simply using it as an example of a pre-filter that uses bio-filter material for small debris as well as preventing large debris from entering the pump. Don't worry about it. I was trying to give you too much information.
You don't have to put an additional pre-filter around the pump. The cage that is on the pump is a pre-filter. In use, the foam is pretty useless. Get rid of it. Your pump is powerful enough it can handle just about anything that gets through the cage except long hair or tough plant fibers. You will see a reduction in water flow from the Savio biofilter if such a thing should happen. If it does, unplug the pump, remove the cage and clean the impeller shaft. Then replace the cage and start it again. If you think too much is getting through, wrap a piece of screen around the outside of the pump.
Your pump probably came with a selection of accessories. Find the tube that screws onto the outlet pipe on top of the pump. There may be more than one size. That is the tube that the hose goes onto that goes to the Savio biofilter. Attach the hose to that tube and put a hose clamp on it. I find it easier to use the more expensive but much easier to attach fittings that rotate by themselves rather than having to rotate the whole length of the tubing to screw it on. The hose goes onto the fitting easier if you put the end into some very hot water and let it get soft. It will tighten up again as it cools. Don't forget the hose clamp. Stainless steel hose clamps are best. Then you can attach it to the outlet pipe on the top of the pump.
I looked at the design of the Savio biofilter and it works just like a Skippy. It is just shaped differently. The description says it has a 1 1/2inch inlet so you will need tubing that size. Since I can't be certain which model you got, double check the size. The outlet is 2 inches on the model I read about. You will need 2 inch tubing for that.

I'm sorry I got carried away. Sandy

Spun nylon pot scrubbers [shaped like a bun] should not get sucked into the pump, unless they break up in pieces. That is virtually impossible.
Some of the older Laguna pumps have an open weave type pre-filter inside the slotted cover that clips over the intake end. This type of filter is even less dense than the spun type nylon pot scrubbers mentioned above and they do not get sucked into the pumps intake.
The newer Laguna pumps have a screening cage that totally encloses the pump. No other material is installed inside the cage by the manufacturer.
The reason for the cage, is to keep hard, solid materials, [such as pea gravel] from entering the impeller chamber of the pump and doing damage.

If you are pumping from the pond to a filter either in the pond or out of the pond and your pump has a cage around it, you do not need to stuff the inside of the cage with anything at all. The pump will handle algae, soft plant material, etc and pass it onto your filter box, where it will be trapped by the filtering material in there.

If you have, as Sandy explained, a small pond of 100 gallons and NO filter other than the cage type, then stuffing the cage with pot scrubbers or a like material will act as a place for beneficial bacteria to colonize on. Though, unfortunately because of it's small size, the cage and filter material you use, will require to be taken out and cleaned at least once a week, killing off the beneficial bacteria. [see note at bottom]
Stay away from soft foam pads, lava rock and those soft flat pot scrubbing pads. They are too dense and plug up too quickly with the algae and mulm in the water.
Wrapping the pump inside quilt batting or any other dense/close knit material, is extremely risky, unless you are willing to check it out continually, as it can plug up within minutes and damage to the pump can take place.

Note.
Your pond's sides will eventually be covered in algae containing beneficial bacteria, after the pond becomes stabilized. So there is no need to worry about washing your pre-filer cage and material out once a week or whenever. Just leave the natural growth on the sides of your pond.
"Horton"

OK, so I should close up my pump housing and leave it as is. And no pre-filtering at all? Thanks, Horton.

Sandy, I am so sorry! I didn't see your message to me before Horton's when I last looked at this thread. You gave me so much good info. I will have to go through it very carefully to set this all up. I hope Sunday or Monday I can get everything ready, or at least ordered.

For some reason there wasn't any foam inside the cage. So no problem there. However, I do have oxygenators all over the bottom of the pond - I hope they don't get in there because the cage slats are pretty wide compared to those little plants. Well, we will see.

What are those fittings called that you can rotate by themselves so that you don't need to spin the whole hose? I want to make sure I use them.

We've made hula hoops before (LOL) so I do know about the warming to soften the plastic.

Thank you so much for being so patient with me.

No problems. I have a tendency to over-explain things. The connectors I like that can be hand tightened are called swivel fittings. I put a link below that shows an example and supplier. Laguna puts out a popular fitting that is a push button but it hurts my double jointed fingers.
I am always surprised that so many people do not know about the hot water treatment. They don't know about using a thermos either. LOL! Sandy

Here is a link that might be useful: swivel fitting

Cool, thanks! They have a few things at that link that are perfect for my pump.

Now, how to get an adapter for the 1.5 fittings to the 3" hose??? (It's always something...)

You don't really need the 3" hose.