Grounded and Fused?

The distro block does not have to be fused.  It is the wires that connect from battery to amplifier that do have to be fused.  And each separate power wire out of the distro has to be fused.  A fused block gives you the fuseholders, but you can also use a simple unfused block and put in separate fuse holders on the wires.

All that to emphasize that the wires are protected with fuses.  An overheated wire can start a fire in the vehicle.  You should have a 4 gauge wire connected to battery, and a fuse close to the battery in that wire.  That fuse can be as high as the maximum amperage that a 4 ga. wire is capable of carrying without overheating.  This chart shows that value to be 150 ampereres.  Now, the thing is...you are only going to draw a max of 90 amps...so you can fuse the main power wire at any value from a minimum of 90 to a maximum of 150.

The individual wires coming off the distro to each amplifier, too, have to be fused.  Again, these fuses protect the wire from overheating due to accidents or whatever that might cause a ground short in a wire.  These wires should be 8 ga.  See the chart for max fusing:  100 amps each.  So the same rule applies as above:  one will be any value from 30 to 100, the other will be any value from 60 to 100.

What is the "Grounded..." part of the post title?  A play on Dazed and Confused?

https://www.bcae1.com/fuses.htm

Everything Stevdart said, but I would only add that I've read (on the link above and elsewhere) to stay away from buying the maximum 150 amp for 4g wire.  They recommend 125, and I have to say it sounds like a decent idea to be safe rather than sorry.  (who knows if brand x 4g will start burning earlier than 150)

I gotta questions, When running a 4 guage to a distroblock, on the distriblock has an AGU fuse slot, We put fill them up with an 80 amp agu fuse.  Is a fuse holder with fuse required between the amp and the distroblock? It'll be an 8 guage coming out from the distriblock. Will most likely use an ANL fuse all around, except the distribution block???

between the amp and the distribution block?  NO ( since the circuit is already being fused in the distribution block )

between the battery and the distribution block? YES     check local insurance regulations but usually it has to be fused within 12 inches of the battery

About the ANL Fuse, Are all distroblocks AGU fuse type? or are there ANL FUSE distroblocks?
THis website that kfr01 have sugggested

https://www.bcae1.com/fuses.htm

I find it to be very useful. Was wondering if they had a page of information on subwoofers, and caps?

As far as I've seen, distro blocks have the AGU fuseholders, because you know that each wire is going to only one amp, and each wire has its own fuse.  You wouldn't need the higher value and more expensive ANL fuseholders.

And type in www.BCAE1.com in your address bar so you can have access to all the pages there.  He covers just about everything, incl. info on subs and caps.