dropping feeders and worms for 4 weeks is a rather bad idea.
If your bichir is off live, you can do the following(you have 6 month to prepare):
1) buy a auto feeder, chose one that allow twice a day feeding and a larger capacity.
2) get some sinking dry food tablet
3) buy a couple pots of pothos
1) wash the soil off the pothos and stick the roots into any opening you have in your tank(or in the basket of your HOB) or see F1's thread on it...if you can find it, PM f1 vet, he will love to preach it to you

Let it grow for a bit
2) put small sinking pellets in your auto feeder, program it for once a day at dawn or twilight. and use it. See if your bichir actually can get some food...if not, program it for twice a day, one at day time once at night.
3) when you get this all setup, do a trial run...monitor if there are actual food left over, if there are, decrease per serving amount until okay.
4) run a few weeks only on this, main while test nitrate to see how bad is the nitrate rise over time...
5) when you work this out(a month or so), spend the next 4-5 month to feed them normally or slightly more to get them a little extra bulk while do WCs normally
6) one week prior to leaving, set this all up again and see how it works, 3 days before leaving, do a huge wc(your fish are not the sensitive ones I worry about)...
That should work...be sure to heed F1's advice about your equipment placement to account for evaporation.