Dude. You're making this WAY too hard.
There's an easy way to get to 200g with each tank bottom within reach.
Just keep the 90 as is.
THEN, use tanks you have lying around, hell I can give you some, and ADD to your current setup.
This allows you to achieve a split level effect AND allows you decorate each tank individually.
I've taken the liberty of making you a blueprint.
No need to thank me.