hi again and thanks a lot to everybody for helping me with Kiyo!!
right now i have him in a 2 gallon tank with NO filter still... but I started cycling the sponge filter by itself in a 3 gallon tank, unfortunately I freak-out when the power filter started spitting out what it seemed the "white hair algae" so I took Kiyo out of that tank and throw away the old filter

... so I am starting all over!!
unfortunately I most leave the city for 5 days 'cause of work so I hope the cycling goes OK without changing the water for a couple of days, I am not sure if I can leave the filter just there, cycling by itself (NO Kiyo there of course!!)... in the meantime I am keeping Kiyo with plenty of water changes since he doesn't have a filter yet in his old 2 gallon bowl with just the 7.5 watt heather and plenty of water changes
I just found the "Prime" product at Petco, so I am picking up tonight for his next water change.
I have been trying to take a picture of the 'white strings' but they are rather elusive
if it's the white hair algae, is that what could be causing Kiyo the fin rot? his eye is now completely recovered!

but the fin rot is still leaving some holes in his lovely fins... could it be the Arrowhead Spring Water with Betta-safe that caused the white strings?
again thanks everybody for your responses and ALL your help!! I am still learning a lot about Fishes but overall I don't want my little Kiyo to be uncomfortable, thanks for helping me giving him a good home
