How often should I change the water in these two Betta tanks? Does once or twice a week sound adequate to keep everything under control?

If you are not using filtration then daily water changes. You need to dilute the toxins that are produced by the fishes waste. Also, dont overfeed. Only feed the fish what it will eat right away. If any food is not eaten right after you feed, remove it right away. Remove any poop or crud daily. Most people use a turkey baster for this in a small tank. If food and poop is allowed to sit it will break down into ammonia. This is toxic to fish and will kill them. There is no safe level of ammonia.

Would the Bettas get along with Corys? I've got two, though I have been considering finding a pet store to give them to. If they'd get along with my Bettas, I'd rather keep them, though.

Yes they should get along, BUT your tanks are too small. If you add anymore fish to the small tanks you will have crowding which may cause aggression between these fish who normaly get along. Worse then the aggression will be the overload of toxins. The water volume is way to small to dilute ammonia excreted by 3 fish. Give back the cory's ifyou can.

Do Bettas actually like foliage in the tank? I bought some silk plants (so they wouldn't tear their fins), but I'm not clear on if they actually enjoy having plants, or if they just don't mind.

Yes. Live plants would actually be a better choice in an unfiltered tank. The easiest plant IME/IMO to keep is a Java Fern. They seem to do good in almost any water condition. Live plants will oxygenate the water and remove the ammonia produced by the fish. If using live plants you can get away with less frequent water changes. With that said you should use water test kits to verify ammonia and nitrite levels. I would reccomend A.P.I. tests, the 2 part ammonia test and nitrite test. These kits should last you 3 years. If you get the less expensive dip strips, they are inaccurate and only last as long as how many come with the kit. In the long run the reagent (liquid test kits with test tubes like the A.P.I.) are alot less $$$.

I may need a heater to try to keep the tanks warm enough. Is a little 7 watt heater good enough, so long as I keep an eye on the temperature?

The problem with the 7W heaters is they do not have a temperature control or thermostat. They are preset by the factory and depending on your tank volume and water flow they could over heat. Better to get a 25W with temperature control. They will not over heat (unless they are defective) because they have a thermostat that will turn on and off the heater as needed. They work like the furnace in your house, set a predetermined temp. and when the water cools down the heater will kick on. When the desired temp is reached the heater will shut off. If the water stays at desired temp. or is hotter then your set temp.(like in the summer) the heater will not kick on.

My last question, do I need filtration, or would a bubble stone suffice? I know they do not like a lot of current, and I'm not sure which option is best.

A filtered

Sorry my lap top was going to die. An airstone will add oxygen as well as some movement in the water which is good. If yu get an airpump that has an adjustment knob you can turn down the airflow if the betta doesn't like it too fast. I had a betta that really like high water flow. He would swim in the filters flow and circle back to do it over and over. Filters also can have an adjustment for flow. You also could use a sponge filter or in-tank filter that uses an airstone to power the filter. They are used for fry tanks where the babies are too small and may get sucked in to the intake of a power filter. Some still use them in larger setups, I have one or 2 like this. A filter will help clean particals from the water and is a place for beneficial bacteria (BB)to grow. The BB growth in the filter is also called the biological filter. It seems that you are a little confused by the "cycle". To better understand I will put a link to a well written article for beginners about the cycle or nitrogen cycle/biological filtration. If you are asking what is better a cycled aquarium / filtered or a "bowl" where you do daily water changes, the cycled/filtered tank is the best (cycled/filtered with live plants is even better), the unfiltered or one that has a live aquatic plant in it is 2nd best, no live plants doing daily water changes 3rd. The advantage of the cycled filtered is that it is more stable and will help keep you fish from disease and parasites. Besides that you don't have to do daily water changes and cleanup poop and excess food immediately. If you want to or have the time it isn't a bad idea. But things like vacations and getting real busy won't be as much of an issue. The fish will probably look healthier and live longer.

Here is a link that might be useful: Begginers FAQ nitrogen cycle from the Krib

hello, I also have Betta's and love them very much. Mine are male and live in large 1 1/2 gallon vases.One fish to each vase.I have bare root plants, ones that can live in water in these vases. The roots are in the water and the green leaves stand up above the water line.My Betta's love to swim in and around these roots and slide in between them to rest, usually near the top of the water. I dont have any form of filtration system or airation, and I have had these for 3-4 yrs. I change the water once every 2 weeks and only use bottled water. I put 1 cup of the original water back in with each water change. Bettas breath air so they need to be able to come to the top, one reason mine are lazy and rest in the roots. Also they will only eat one tiny pellet of food a day. So I tap the glass before I drop a pellet in to get their attention, and they usually immediately swim to get it. I have my Betta vases in different locations around my house. One in each bathroom on the vanity,one on my diningroom table and one beside my favorite reading chair. I find they are great company. I hope this info helps.Any questions please email me. Ari

I will not argue that keeping a betta in a vase with a non-aquatic plant will not work. The fact that Ari has kept them for 3-4yrs this way. This does not mean that it is the best way, or only way. I still believe that a cycled,planted aquarium is the best chance for its health and longevity. Climate has a role, for instance those that live in FL can get away with this because of the climate. Room temp. water is not ideal for the betta or any other tropical fish. They will eat like pigs andbe allot more active in proper temp. water. More importantly they will not be as susceptible to parasites or disease.

When I was about 11, I kept a betta fish in a little bowl of perhaps two cups of water. He got fed every other day, and he was lucky if I changed his water every two weeks. At the time, I didn't have any idea that I was abusing him, since I didn't know about ammonia and temperature, etc, and I was told they actually liked not having enough room to turn around. That poor little fish lived for a year and a half like that. When I think about it, I feel sick to my stomach. It's like being forced to live in a cold closet with your own waste piling in the corner, and only now and again does someone grace you with their presence to give you food and clean a bit. Bettas, like humans, are very durable creatures, but that doesn't mean that they should be kept in poor conditions.

Your 2- and 2.5-gallon tanks sound great for bettas, and you can get Red Sea Nano filters for them. I use one in my 2-gallon on the lowest setting, and my betta is happy as can be. Bettas do love plants, and anything else that can be used as a hiding space. They're very curious, and they love to poke about and explore. If you get algae, you can add physids (pond snails) to eat it. Pet stores always have a multitude of the little guys, and they'll give you as many as you'll take for free. Bettas like to poke at them, and some will even love to eat the baby pond snails. (Physids will have as many babies as they think their environment can support.) Remember to have some kind of lid for your tanks since bettas are jumpers.

my mom said i can have a betta as long as i do all the research on them but i dont know how big of a tank she will allow. Do bettas need a certain size tank? Do I need a filter? And do I need a heater?