growing in an aquarium posses so many problems. your plants will probably outgrow the aquarium, and you will have to move them out of the aquarium, so theres no point to using it to begin with. the aquarium will tend to make the plants environment more humid than is required, then u will face problems with mold and rot.
as for you MG soil, add at least a third perlite or vermiculite, this will help with drainage and soil airation.
a handy trick i use for some of the weaker or more spindly hybrids, like WW, is to grab a bunch of straws from your local Mcdonalds. cut the straw to length, then cut the straw length wise so u can "wrap" it around the stem for support. then punch some holes is the sides of your pot at the top and tie the straw supported plant upright, works great for me.. i would also grab a small fan and have it blow gently on your plants. the "wind" causes the plant to sway, creating tiny micro tares in the plants stem fibres. the plants reaction is to focus more growth to the stem to stregthen and support the plant as a whole.
good luck!!
good luck..