Takshaka

I'm growing in a 7 gallon bubbler with holes for 6 plants (I have less floor space than 'air' space). I realise that this is small for the number of plants, but there will be fewer when the males are removed.

What I am wondering is if I can regularly trim the plants roots so that they have enough space and so that they don't get tangled in each other (and make it difficult to remove the males without leaving dead roots behind).

So my questions are, how extensively can the roots be trimmed without causing problems? Which parts of the root can/can't I trim? How regularly can this be done?

Thanks