All filtration boils down to turn over rate. After turn over rate what ever media you want to run is your choice.
Your tanks are 270 gallons a piece. So HOB style filter are pretty much out of the question for decent filtration.
So you are left with canister filters or sumps. The fx5 is a really nice filter. To have good filtration using fx5 canisters you will need 2-3 per tank. And that means spending 1200-1500+ dollars on filters alone after you buy the media to fill them with. ( fx5 at $250ea + media) A good turn over rate to aim for with canister filters is around 6-8x per hour. (270g X 7=1890 GPH of filtration) And 2 fx5's does not come close to this. But 3 does

so make it 3 fx5's per tank.
After you get out of the hospital and fully recover from that stroke proceed to the land of sump filtration below.
Or you can build 2 DIY sump filters out of old 55g tanks. It is a very simple process. It looks overwelming at first but after you make the desicision to do it is very simple.
A good turn over rate for sump filtration is 3-5 times per hour. And this is because of the larger amount of mechanical media to clean the water and the large amount of biomedia that sumps can hold.
If your tanks are not drilled then you will need some very cheap and unattractive DIY pvc overflows that can be built for a few bucks. Or buy some hang on the back over flow boxes. I use the HOB style overflows.
Then all you need is a pump or pumps to meet your flow and turnover demands .
There are easy to follow write ups all over the internet for building a sump filter so i won't go into detail about it.
I would think that you could build a nice sump for that size tank for less than 300 bucks plus some scrubbies and poly floss for media. And that includes a new pump and overflow box. Or if you search around for deals and used equipment you can probably cut the 300 in half.