Yes. This is why I always plan to hatch on Sundays.
WAY TOO SMALL!
Granted these figures are for standard-size birds, not bantams, but the recommendations are,
For the first week or so, 1/2 square feet per chick.
For the next couple weeks, 1 square foot per chick,
Up to 6-12 weeks, 2 square feet per chick.
After that, the full 4 square feet per adult.
The figures aren't firm because birds, climate, and management systems vary, but I have chicks off heat and integrating into the flock as early as 3.5 weeks in hot weather and I always find that they use every inch of space available.
Also, aquariums are heat-death traps unless they can be VERY tightly monitored.
If you can possibly brood outside in the coop that's probably the best option. They get plenty of space and plenty of fresh air (coop should be designed to eliminate drafts at floor level even in our warm climate).
Yes, a heat lamp *can* be a fire hazard. But if used in a safe manner -- hung by a chain, correctly adjusted, at a proper distance from anything flammable -- it can also be an excellent choice for raising chicks.