Can I trickle charge while using my battery with a .3A 12V aquarium pump?

[AndyInNYC]

I have a battery on my deck powering a .3A 12V aquarium pump to feed a strawberry tower.

Can I attach my trickle charger:

a) with the pump/timer still attached?
b) with the pump/timer still attached and actually pumping water (ie drawing power)?

I know diddly about electricity and I don't want to either kill the pump/timer or the battery.

Thanks.

Andrew