Fish care Qs - Flakes vs Pellets, Activated Carbon or not, Cleaning Filters..and the tank?

Howdy... While scrambling about seeking information on treating a sick GloFish Tetra I came across topics which have a ton of information and seem to be greatly debated...enough so that I wonder if I should change how I do things for my fish. Sadly that fish died. I had him for 3 years. His name was Peaches bc of... show more Howdy...

While scrambling about seeking information on treating a sick GloFish Tetra I came across topics which have a ton of information and seem to be greatly debated...enough so that I wonder if I should change how I do things for my fish.

Sadly that fish died. I had him for 3 years. His name was Peaches bc of his color.

Now for my two remaining tetra ...if Im doint something wrong...I want to fix it.

Ive had fish for a while and do know stuff...but never claimed to know it all. Honestly, I never really came across these topic.

First: Flakes vs Pellets - for my smaller fish I have always used flakes. I didnt know that many folks say "Dont Use Them. They're bad for the fish"...both for what happens to the flakes inside the fish..and their potential for causing swim bladder problems bc the fish might gulp air while eating them from the top. To that effect I tried feeding them a couple pellets last night. One of them nipped at it curiously. The other tetra ignored it. Today the pellets were stuck to the side of the filters water intake tube and the other was broken apart at the bottom of the tank. They were medium pellets. I thought of getting the small pellets...but if the fish didnt go after them, they would eventually sink down and get lost in gravel cracks. Yes, I know there are sinking and non sinking pellets. But really...for my tetras - which of these 3 types of food would you use?

- Continued -
Update: Second: Activated carbon or not - I have always used a filter that used the cartridges that have the activated carbon inside the pouch. I didnt know there was the great debate about whether to use it or not. I did know that the AC has a short term...but you cant replace it without replacing the whole... show more Second: Activated carbon or not - I have always used a filter that used the cartridges that have the activated carbon inside the pouch. I didnt know there was the great debate about whether to use it or not. I did know that the AC has a short term...but you cant replace it without replacing the whole cartridge...which would kill your beneficial bacteria in the white filter media. I know that you have to remove it for a hospital tank, but is it really important for the care of your fish or not?
Update 2: Third: Cleaning the filters and the tank. Again...I use the filter cartridges. In a short time the AC becomes ineffective...and a eventually the white filter media gets gunky. To replace either means killing off the beneficial bacteria and starting the tank cycle all over. As far as cleaning the whole tank... show more Third: Cleaning the filters and the tank. Again...I use the filter cartridges. In a short time the AC becomes ineffective...and a eventually the white filter media gets gunky. To replace either means killing off the beneficial bacteria and starting the tank cycle all over. As far as cleaning the whole tank goes....even if you do vacuum the substrate..eventually there's particle build up in the gravel and maybe the rocks themselves need cleaning and the corners of the tank, etc.
Update 3: Whats the best way to deal with these things for my fish?
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