I'm very interested in the fire kasina practice but I wonder if a retreat is fundamental to really get it going. 
It is possible to have good progress if I only practice once a day for 30min?

Right now I'm focusing the morning practice on Jhanas for 40min + 20min of Vipassana, so the fire kasina would be done at night before going to bed.

Thank you!

Yes, progress can absolutely be made with low dose, daily FK sits. One of the great things about FK is that you can get excellent effects with very short sits (20-30 mins).

However, you might eventually find you naturally want to spend longer navigating the murk phase and increase your sits to an hour or two. 

Enjoy! 

Thank you Anna!
I will give it a try
;)

Are you doing well mixing practices (vipassana+kasina)? I can only practice kasina at night, would love to add vipassana in the morning.(Sorry for my english)

off:Sorry to ask, what is your native language? Can't find a way to send this question privately lol.

That is like asking if doing exercise two times a week is enough.  It depends, if you want to be pro athlete then no. If you want to be in shape, maybe.

I think yes, it is enough. Altho i would go for at least 1 hour.

Ok so 1 hour at least once a day can have a good inpact on progress. Check. 

As there is a dreamy aspect to the Murk I wonder if night time is better suited. Very well might be as there will be more inclination towards such feel naturally.