I have a small bowl to keep fish one, i want to have some small fish, i not sure whether small fish like guppy or tetra can live inside it without filter and aeration or not. I mean if i put one or two fishes only... Thank for any advice

its ok to keep. Jus keep an eye on the ph of the water. do weekly change of water.

Thank, are you mean either guppy or tetra is okay in the small bowl?
I not sure whether it is true or not, tetra need rain water to survive, told by LFS (I a bit doubt).

guppies would be better coz they are easier to keep and does not really need filter and stuff if u planning on just keeping a few.

bout the rainwater, i think not necessary. aged pipe water will do.
rain these days acidic hehheh

i dont think so man....cos as far as i no both guppies n bettas dont have the Labyrinth organ(an organ some fishes such as bettas and gouramis posess which acts like a lung and can take oxygen straight from the air)...so i dont think it wud b a gud idea keeping them in a bowl wfout aeration....n also(trust me...iv learnt from expirience)...its not gud to put an air rock in a bowl....current is too strong...unless u can find a weaker source of aeration....my first fishes wer 3 neon tetras in a 2 1/2 gallon fish bowl....all 3 died in 3-4 days time...da best fish to keep in bowls r bettas man...dey just refuse to die man haha...n also u shud tell us how big ur bowl in...in my bowl i had 1 male betta and 2 gouramis....dey did very well....now moved them to a 15 gallon tank...if ur starting out in da hobby i suggest u invest in atleast 15 galloner...go jalan pasar man...not very expensive...80 bucks can get tank wf filter all...good luck!!

PS : guppies n neon tetras arent da best fish for beginners....esp in a fish bowl...strongly suggest u get a betta