Glass minnows and silversides are anchovies. Yes, the same anchovy that you eat on pizza or in Caesar dressing. The bay anchovy is Anchoa mitchilli for those of you that hope to catch me in my identification mistakes. They range from Maine through the Gulf of Mexico in great abundance. They are easily recognized by the fact that they are transparent with a broad silver stripe down the side and are seldom over three inches long. There are a half dozen species according to Dr. Bob Shipp and he says no one but a fishery scientist would care to describe the differences in them. When you are looking for bait and suddenly your fish finder shows a giant school under the boat, you throw the net perfectly, it sinks quickly, and comes back empty, you throw again and again as the fish finder tells you to, and continue this game until you are exhausted - then you are throwing on glass minnows. Some of us play this game for many years, even though we know better. Eventually you will get older and either find a younger person to throw the net, or after one or two empty throws, move on to another area to hunt bait.
There are ways to acquire glass minnows, because they are great chum material. The simplest is to buy them in frozen blocks at the tackle store, but you can buy a small mesh cast net and catch them yourself if you are a purist, (or bored silly). The net will be nylon usually and has a mesh size no bigger than 1/4 inch. They really aren't that expensive to buy and you will be using them dead anyway. I have never seen a baitwell that would function properly to keep a batch of bait that small alive without clogging up constantly. The best way to use them is as chum. Cut them into small pieces with a pair of stainless scissors and drop a steady stream of the pieces overboard into the current. You can do this while you are slow trolling but I think it is more effective to chum from an anchored position into the current behind the boat.
You can use the same pieces for bottom chum simply by dropping them overboard in your chum basket and letting it sink to the bottom to disperse it where you are fishing. You can also just place the frozen block of glass minnows in a mesh bag hanging over the side of the boat and let them thaw and drift in the current. This is effective, but you use a lot more minnows than you do by cutting them. Don't forget, you want to attract the fish, not feed them. When they are full, it's hard to get them to take a bait with a hook in it.