I have my betta in a 2.5 gallon tank and I have heater nor filter. I think since you have a bigger tank than mine you should get one. But bettas don't favor water flow(at least mine doesn't) as much as other fish. I saw this filter earlyer and it is for a one gallon but it does't have as much a powerful flow so your betta can swim to the other side of the tank to escape the flow. As for feeding him on only freeze dried blood worms, I think you should feed him a small ammount of that and another type of food, so he can have a balanced diet. Hope this helps!!!
Morgan

Here is a link that might be useful: Petco mini filter

Ezzy,I'm no expert so don't take this as though it is written in stone.
I believe that a filter is a good idea for your fish aquarium. At least that's what everyone has advised and it seems to be supported by all that I have read thus far.

And to echo Moregirl,I think that a blanced diet would be far more beneficial than the worms alone.
Good luck.

Yes, deffinately mix it a bit. Get some frozen foods as well. I am finally going to start that brine shrimp hatchery to offer live food. I learned the hard way by getting a little lax in the food department and it may have resulted in recent deaths of healthy fish.

Thanks for all your help guys, i'm going to take a visit to the local pet store to see if frozen food is available. I've heard that pellets are also nutritious but bettas don't like to eat them... should I give them a go?

I fed all our bettas a small tiny floating pelleted feed made for betta and they love it. I also supplement their diet with bloodworms and other types of stuff. I think unless yur going to do regular water changes even a betta needs a filter. You can get a small NANO filter for a few bucks with a variable flow control on it that hangs on the back of the tank and its mush better than no filter at all IMHO......My local marine store dealer has been clearing out any items that are scaled down to tanks of 10 gal and less, at unbelieveable prices, due to the lack of interest in this area in small saltwater pico tanks, so needless to say I have been getting a lot of good items for practicaly any money. So good in fact I have been getting these NANO powerfilters for $2.25 each which turnover 60 litres per hour, and with adjustable flow they are a most welcome addition to all our betta tanks.........and my water changes have been reduced as well.The local LFS chain store here sells these same exact filters for $12.95....HBT, Hikari, are just two companies that make good balanced betta pellets. Bettas are carnivores and prefer a meaty diet, but I have some that will also take flake tropical food as well. I also feed ours tiny shredded pieces of shrimp from time to time.

Definately give the pellets a go. My betta doesn't see much of a difference between the foods! I've never had a nano cube before, but I have heard good things about them...I still recogmend the mini filter- it would help to reduce the water changes.

Thanks for your assistance, i've put a filter (two settings, high and low... not really sure about power and all that but they said it was for a 2.5 to 5 gallon tank) in the larger tank and my betta actually seems quite thrilled with it... still working on an upgraded tank for the other one though..

A filter isn't necessary for a small tank like a 3.5 housing a betta, but since you have one, you should start monitoring the chemical levels (ammonia and nitrites) because having the filter will start the cycling process. You can cycle a 3.5 gallon, but it's less stable than a 5 gallon and up. You can go filterless for any betta tank that's 5 gallons and under. Just stay on top of water changes.

With the filter in your 3.5 you'll have to do 100 percent changes and scrub the bacteria off the filter pad to avoid cycling. If your fish starts showing signs of distress like being listless, spasming, or getting red streaks through his fins and body, ammonia and nitrite levels are too high and he will die. (Ammonia and nitrite spikes are a normal part of cycling, but very dangerous for a fish.) It's up to you whether or not you want to keep your filter. Me, I would toss it unless you got a 5 or 10 gallon tank.

Also, pellets are good for your fish. The highest quality one is Hikari Betta Bio-Gold.

Ok Minaku, I've removed the filter from the tank... it holds about 12 litres which equates to about 4 gallons but it isn't filled to the top. The whole ammonia and nitrate thing scares me a bit and I don't think I'm really ready to dea with that right now. Also, how often should I change the water in the tank, is once a week enough? And should it be 100%? or what ratio?
p.s (i've also ordered some hikari bio-gold online)

You should do a 50% change every week, and keep a turkey baster on hand to suck out the poop and the food that falls to the bottom. Every 2-3 weeks do a 100% change - I'd err on the side of 2 weeks. If you can, buy yourself an ammonia drip-tester that tests only for NO3 and see when your ammonia levels start showing up. That's when you know you need to do a water change.

Any time you start the nitrogen cycle in a tank with live fish can be deadly. The size of the tank shouldn't matter to sucessfully cycle as long as it has a heater and you have pH, Ammonia, Nitrite, and Nitrate test sets. Ammonia test strips are easily skewed when testing during the cycle. Besides they are a little expensive. A reagent type is best. Products like zeolite and Prime along with frequent water changes during the "cycle" will help reduce huge Ammonia spikes durring the cycle. Fact is a filtered tank no matter size is more stable then huge water changes without the help of beneficial bacteria. Ammonia,Nitrite and Nitrate can be allready present in tap water. It would be wise to let your filter run in an established tank (freinds or petstore) for 2 weeks or beg, borrow or steal filter media from an established tank.When an aquarium is cycling no harmfull ammonia or nitrite will be present( I should say detectable). Another possibility is upgrade to a 10 gal. for both bettas and use the 4 gal for a QT tank. This will allow for some "buddies". Do a fishless cycle with the 1st tank and then put a betta in. Let the filter of the next tank run along with the one in the first for 2 weeks and fishless cycle the 2nd. I always keep extra sponges in my show tank just in case.

I'm a bit worried now regarding this nitrogen cycle... I had the filter on for two days, with the fish in the tank, before removing it... and don't have a test kit or anything... should I do a 100% water change?

I think you'll be just fine. Do water changes as per normal. If you feel really nervous, a 50% change will be okay. :) Don't worry too much!

Ezzy if you do water changes frequently your aquarium the betta should be OK. Having a bare tank (no filter, gravel, and decorations)the tank will not start the nitrogen cycle because there is no surface material for denitrifying bacteria to grow. This is an acceptible way to keep the betta but it is not the best. Ammonia will accumulate in an uncycled tank day to day so more maintainance is required to remove poop and food on a daily basis. In a cycled aquarium the ammonia levels stay so low they can not be detectable. No ammount of ammonia is safe especially in water with higher pH. I would look into a fishless cycle for down the road so you could try the plants and other fish if you are still interested.

I have placed a small decoration, fake log, for my betta to play in... I hope this won't affect the nitrogen cycle thingy :(
I should probably get a book... though you guys have been wonderful... i'm so paranoid!
So if I wanted to cycle... I should do a fishless cycle... for how long? like 2 weeks or so?? And then once everything has calmed down add the fish? Is that how it works?
Thanks so much for all your help

No, anything that's aquarium-safe shouldn't affect the cycle or the pH unless it's driftwood that hasn't been fully cured or slate, which will affect hardness.

To cycle, keep monitoring the chemical levels. Your tank is cycled when you show 0 ammonia, 0 nitrites, and a low level (say 20) of nitrates. This may take anywhere from a couple of weeks to a month or more. Often if you get BioSpira the cycle is established in days, but you do need to keep it cold as the bacteria in the bottle will die if they get warm and have no food.

Try this link for nitrogen cycle explained. Read the first 5 articles. They are a bit involved so take your time. The fishless cycle method used here works well.

Here is a link that might be useful: Bio-Chemistry 101