I just got my new male betta fish, 3.14, 2 days ago.
I bought him a 2.5 Gallon Beta mini-bow kit. It has an under gravel filter, and I bought a hydor mini heater to go with it. I am getting so many mixed opinions on having a filter it is mind boggling

. Do they cause more harm then good? I have no problem doing more frequent water changes if that is the only benefit of having one. The current seems to be kind of fast to me butI really have no clue. There is no way to turn down the filter either.
I read on the FAQ that a heater was an absolute, but it's hot where I live right now and his tank is staying around 80 without the heater installed. Our house is kept at 78 except during the day it goes up to 85. Will those changes be harmful to him? Should I install the heater?
And are the marbles an okay bottom for him or does he need to have gravel?
Thank you!!
Here is his current set up.