1. Originally I was looking at a cute little 3.5 gallon tank but quickly realized a 10gallon would be better, but I know form experience there are many who will tell you that you need a bathtub for your guppy. So is 10gal overkill for 1 Betta and is 3.5gal really too little?
depends on who you ask. PETA will tell you a 20 gallon tank isn't big enough. If you just want the betta then a 3 gallon is fine but if you want tankmates - go with the 10G. One betta would love a 10G to himself as well.
2. I'd like to have live plants in my Betta tank, but it is going in my office which gets very little natural light. The tank would have LEDs and the office is lit with florescents. Should I even bother trying with live plants?
There are low light plants you can get - anubias, java fern and most crypts are low light plants. Check out the planted tank section before you get plants though.
3. If I can do live plants, what are good varieties that Bettas prefer and what ones should I avoid?
Petco and Petsmart sell some plants in a plastic tube claiming they are aquatic plants. Abut 80% of the ones they have are NOT aquatic. The ones that I have seen that are - Anubias, Amazon Sword and wysteria.
4. I'd read that you can have 1 male and two females and other places say that's really bad. So which is it? Is my Betta-to-be sentenced to a solitary life in his little world?
I do have a male in with 5 females but I also have a 20 gallon planted tank and they have been together since they were juveniles. He was labled as a female and since he was very young, I though he was. However, I NEVER would of put him in with the females if I had known his gender at the time. Normally they get more aggressive as they get older. He did not. if you have a 10 gallon tank - you can get other fish species OR if you do some research on female betta sorieties you can go that route. Be forwarned - females can be just as aggressive as males and you may end up with a lady or two who can not be kept with her own kind.
5. Do Bettas get lonely? What other fish would work well with Bettas in a small tank?
I think they are loners for the most part. Like I said above, you can do some other species - like cory's but you need a group for them to be happy. I'm sure there are others that can go into a 10 gallon with bettas but I don't know what they are.
6. What sort of tank cleaners (algae eaters, snails, etc) work well in Betta tanks?
If you have some serious filtration, you may be able to get away with a BRISTLENOSE pleco
. I have heard they can be kept in a 10 gallon tank and they are supposed to be the best at algae eatting. They don;t get very big - maybe 4 or so inches. If you find one in a store make sure it is NOT a common pleco - they get to like 2 feet
Snails or shrimp are good too but the shrimp might get eatten by the betta. Perosnally, I love snails - just not ones that are hermaphrodites. Apple/mystery snails are pretty popular and come in a variety of colors but they are poop machines.
7. When I go to cycle the tank, can I use one of the used filters from my other tropical tanks to help or is that going to be a bad mix of bacteria for a Betta?
Yes you can
8. I was told that Bettas are weak swimmers and can get caught in the filter's pull. Should I use a filter that is rated for a smaller tank (ie: one of those small 1-3gal tank filters in a 10gal tank) or just forgo a filter entirely?
It's up to you but if you are doing a 10G - go with a filter - especially if you want tankmates. I stuff sponge for the aquaclear filters into the outflow part of my Aqueon filters. I also stuff it inside the filter itself and forgo the cartridges that they say to replace every month. If you toss those cartridges - you are tossing out the bacteria you want as most if it will be in the filter. you can also just rinse the cartrisge in used tank water once a month or so but i noticed the filter floss or whatever they are made out of falls apart quickly. The Aquaclear filter sponge lasts ALOT longer.
If its 5 gallon and under, i skip the filter and so the 2 water changes a week.