80% of my Danios are pregnant! Help!

danios don't get pregnant. they get egg-heavy.

not much you can do to stop them. they'll probably eat their own eggs.

Odds of eggs and then hatched fry surviving in a community tank are like .001%.

Now if you want to keep the eggs and try to hatch fry, you'd need to move the danios to a separate tank and after you see them spawn, move them out of that tank.

If the females are looking pretty plump, you may want to isolate just a single female and male in the 5.5. They don't guard eggs or anything, they just scatter. The only way to know if they have spawned is that the female will become slim again. If you could get something like java moss to line the bottom of the tank, or even large sized pea gravel, that would allow the eggs to fall and not be eaten by the parents.

My danios generally spawn in the morning before the lights come on but where there is ambient light from the room - I'll see the males all chasing a female around the bottom of the tank and the cories happily munching eggs. Now in the process of planting my tank, I left the lights off for several days before the plants went in. During that time the danios spawned constantly. You might try leaving the lights off to encourage them.

Are you shure they are Gravid (egg heavy)? Often times a fat appearance in danios can be caused by constipation.