Welcome to the forum.
First things first, you MUST read this: I just learned about cycling but I already have fish. What now?! - Aquarium Advice
You've got a couple of issues going on here. It seems you understand that you need filtered tanks, but I get the feeling you don't really understand what "cycling" a tank entails. The link will help you see what's going on and what you need to do.
I highly suggest you go on-line and order yourself an API master kit. You can get this for less than $20. If you're in the US, I recommend Kensfish.com. He has them for about $17 and has great customer service. It's very important to find out your water parameters for ammonia, nitrite, nitrate and pH.
Since you have fish, depending on the parameters, you may need to do daily water changes. The ammonia and nitrite will make the water toxic.
What size tank is the split betta? They really do best in 5 gallons minimum. They need a filter and a heater, too.
It's vitally important to know what species you have. You need to find out what those catfish are. The various species have different needs and schooling requirements. Some will also outgrow your tank. Don't trust the lfs
to tell you what the fish is, prior to purchase you should be doing your own research.
If you've got fish in the 10 gallon then yes, you need to replace the filter. The pregnant fish can stay in there and you can use that tank as a grow out tank for the fry, if you wish. That said, I keep my fish in the community tank when they give birth. I have plant coverage for the fry, so I don't have to be bothered with grow out tanks.
75: blood parrots, featherfin cat, emperor tetras, turquoise rainbowfish, BN plecos, japanese trapdoor; 46: WCMM, gold inca snails, ghost, bamboo & amano shrimp, kuhli loaches, rummynose & ember tetras, endlers, platies, flame gourami, guppies; 16: pygmy, peppered, loxozonus corys, otos, assassins, RCS ... ~ Research PRIOR to purchase.... ~