1.) I have a 5.5 gal tank with a bottom feeder (forget what kind, pretty sure a pleco?), a Dalmatian mollie & a tetra.
2.) I also now know the tetra is a schooling fish, another reason to upgrade since I don't think I should put another fish in this tank.
3.) Should I be feeding them only once a day? What about fasting them a day a week?
4.) CYCLING/CLEANING: Should I be doing 10% once or twice a week now? Also, what kind of water conditioner should I get to add to the tap water that will be introduced to the tank? For my tank, how often should it be cleaned once cycling is complete and how much of the water should I change? Should I leave fish in the tank while cleaning?
5.) PLANTS: Any suggestions what types, if any I should get?
Hello, and welcome to the forum and the hobby! Without further adue, let's get started on your quesions:
1.) You are overstocked, no ifs ands or buts about it. However, it's an easy fix - Craigslist and any other classifieds website (in SLC, Utah, there used to be a great classifieds page sponsored by the local news agency, KSL) are great places to go for entire setups for pennies on the dollar compared to new gear. You should be able to double the tank size to a 10 gallon for $50 or less. Meet in a public place, ensure that everything turns on via an outlet, if you can get to one, and check for things like the integrity of the silicone sealant on the tank corners, the integrity of the top and bottom trim pieces.
2.) When adding fish to whatever tank you end up with, use your 5.5 gallon as a quarantine tank. Put the new fish in the quarantine tank for a week or so, and then if they're still alive & healthy, add them to the main tank. And only buy 3 at a time or less, as adding a large amount of fish at once can cause a mini cycle. I would add a few more tetras, and maybe a snail or three, but that's about it.
3.) I feed twice a week, sometimes less. Fish are definitely not used to getting food every day in the wild, and on long vacations I don't feed them for up to 2 weeks. Also, try and mix up their food a little, between veggies and protein. A straight diet of protein can cause constipation (just like in Humans), and flake food is mostly protein. You can blanch some zucchini, spinach, or other lettuce and hang it on the tank wall or just drop it in, and your fish (especially the pleco) will thank you. Be careful not to feed too much (freeze the rest for a later date), or it will go to rot and foul the tank.
4.) Loaded question, depending on which plants you add - in a standard tank with plastic decorations, I would change 50% of the water once a week. More frequently when cycling. The only time you don't want to change that much is if the water looks cloudy, indicative of either a bacteria bloom or green water (algae). You can tell whether it's bacteria or green water by dipping a paper towel in the water and checking the water color against a white background. Also, with no plants with a root system, I would vacuum the gravel once a week as well. To vacuum, I would start the siphon (using my mouth), and then stick the large end of the siphon into the gravel and move it around. You'd be surprised how gross the water is when you suck out all the mulm in the bottom of the tank. Then, use the spent water to water any house plants, garden, etc. you might want to do (plants LOVE fish waste, check out a neat farming style called Aquaponics).
With that being said, the more plants you add the less water changes and vacuuming you'll have to do. Plants with a root system clean/aerate the gravel for you, and actually are healthier the dirtier the gravel is. Plants like moss, ferns, etc. that have shallow or no root system but absorb most of their nutrients from the water make it so you don't have to change water as often. In my full planted setup, I've never vacuumed the gravel (tank has been running 3 years), and I change 50% of my water once every 2 to 3 weeks.
Stress Coat and Stress Zyme are great additives, the only thing you'll need is a Tap Water Conditioner, and it will be labeled as such at the store. I've heard great things about SeaChem Prime, but it's expensive. I use API Tap Water Conditioner.
And leave the fish in the tank. They'll be totally fine. But watch out about accidentally bumping the pleco - they have spines in their dorsal and pectoral fins.
5.) Plants! Yay! For ease of use, get something like Marimo Moss, Java Moss, or Java Fern, as stated. They grow anchored to things like driftwood and rocks, and require a simple liquid plant food dosed directly into the tank (such as API LeafZone or SeaChem Flourish). They do a great job of eating ammonia, nitrite, and nitrate, as well as some of the lesser nutrients like phosphate and sulfate. You might get some hitchhiker snails with the plants - let them go! They'll multiply until the tank is clean, then their numbers will dwindle to match the food supply. They might be unsightly at first, but give them time. Alternatively, you could harvest a bunch of them (use a piece of blanched zucchini and when it's loaded with snails, grab it and throw it in a bag) and send them to me or someone else with a goldfish
Lastly, some tips -
Get a piece of driftwood for the pleco, they like to rasp on the wood, and if it has a cool hidey hole they'll make it into their cave/lair.
Get a light timer at the grocery store so you can give your fish/plants a good daylight cycle. I would suggest only running the lights for 6 to 8 hours a day to prevent an algae bloom.
Get rid of the carbon in your filter. Keep a bag or three handy to strain out medications if you have to dose them, but if you're adding live plants carbon can do more harm than good. It absorbs nutrients from the water that the plants would benefit from, and old carbon can leech toxic levels of phosphate into the water.
Let us know if you have any further questions! Hope this helps.