Ego sum Alucinatio
Moth Feathers
Pet stores are not a reliable place for information. You need to always do independent research before getting any pet, especially fish, because their entire environment pretty much depends on you.
How much bigger is 'bigger'? Assuming you have a common pleco (the most common kind, and most likely that you have), they need at least a 75+ gallon tank, preferably 100 and more gallons though because they grow over a foot long.
"Glow fish" are genetically modified zebra danio. It doesn't matter what color they are, they are zebra danios. Zebra danios need to be schools of 6+ and are very active, needing more like a 20 gallon long than a 10 gallon.
I won't say you're doing nothing wrong..your bioload is really high for just a 10 gallon and the water changes aren't big enough, so the parameters are probably pretty out of whack
(which although it's common, isn't exactly normal/preferable to have). Once you fix those things you should notice the tank not to be as dirty.
A filter normally comes with a couple parts. One is the carbon cartridge, which is usually something with a piece of plastic with tiny slots (kind of like mesh) in it on one side and blue fluffy material on the other side. If you rattle it, you can hear the carbon inside. Carbon isn't needed for aquariums but if you choose to use it, then it should be replaced monthly (or more often, if the tank has a high bioload) because once it becomes saturated it will start leaking out all the gunk it's collected.
The other is the filter pad, which is usually a square of plastic fibers, like a sponge. It holds your bacteria. You never need to change it, but it will collect coarse particles from your aquarium (dirt and stuff, called mechanical filtration) so it needs to be rinsed occasionally (however often is up to you, just whenever it gets dirty) in tank water (never tap water, the chlorine kills off your bacteria). I try not to rinse it -in- the tank because all the stuff you rinse out of it will just get sucked up by the filter again...rather, when doing your water change, when you have the bucket of water you're throwing away, rinse it in there.
Some people also like to use filter floss, and it's cleaned the same way as the filter pad.
I worked at a vet, and got a lot of the information from someone who also worked at a pet store. I figured I was doing pretty well
I was going to get a GIANT tank that's on sale for $100, because the wooden stand is missing a door. It's either 50 or sixty gallons, and thin. That should be good for the next couple months as the pleco grows.
The filters I buy... They have carbon in them. The instructions said to change them out as soon as the carbon meter turns from white to red, which happens monthly. I also have a "scrub" pad, which is just a bunch of lines sticking out of a piece of plastic. I rinse that out every day and put it back.
SO, I went out today and got four more of the danios. I now have five. I didn't want to risk getting any more. The fish all "seem" fine... They're all active, and even school together a lot and chase each other around.
The pleco... Do you know how long it'll be before it needs 100 gallons of water? And, should I use more than one filter? (Like, two 100 gallon filters, as opposed to one). Also, at that point, should I buy a bubbler?
Five is good. I would try to upgrade to at least a 20g for them as soon as possible though. Your tank is really, really crowded.
A bubbler is for aesthetic purposes only, filters provide enough aeration in the water.
You can use multiple filters if you want to. I prefer multiple filters so that I can change the filter media regularly and not have to worry about starting a mini-cycle. They don't all have to be 100g filters though, you could have like a 100 gallon filter and a 20 gallon filter, and so on. My 75 gallon is currently using one for 60-75, a filter for 15-20, and a filter for 5-15.
Also, keep in mind that large tanks (50+ gallons) work a bit differently as far as filters go. Most small tanks use hang on back filters (HOBs), which are fine for small tanks. But when you get into bigger aquariums, you really need a powerful device to move all that water, so it's recommended to use a canister filter. They are quite expensive but work very nicely.
Of course, you don't have to, but if you choose to stick with HOBs (and it is quite hard to find HOBs for large tanks, it was a struggle for me finding one that was even rated for a 75 gallon) then you'll either need quite a few of them or will need to do more frequent, larger water changes.
Oh, and for your pleco:
if you keep your parameters right (ammonia and nitrite 0, nitrate under 20) then he should grow pretty steadily. When his size is too big to be comfortable in his tank, or when he's producing so much waste as to be impractical in that body of water, he needs to be upgraded.
You can upgrade before then, of course.
The thing is, if you let the tank parameters go bad, his growth will be stunted and he'll never really 'grow'. So keep the water clean, feed him a varied diet.