New here - Choosing tank size

Hello guys,

I am new here and happy I joined this community.

I currently have 55 gallon saltwater tank with corals and fish, crabs, snails, etc. I have two powerheads of which one is good with flow-strong and in general flow is good in the tank. I also have Fluval Filter and Protein skimmer as well as Manado Live rocks. The tank has been running almost 2 years, everything is good except that I am experiencing red algae pretty often.

Now I am thinking to upgrade my tank to 120 OR 125 gallon and not sure about the right measurements of both tanks which would be more preferable for both, reef/corals and fish.

First option: 125 gallons

Tank Dimensions: 22"L x 72.5"W x 23.375"H
Stand Dimensions: 18"L x 72"W x 28"H
Environment: Freshwater

Second option: 120 gallon

Used For: Freshwater, Saltwater Fish
Shape: Rectangle
Aquarium Dimensions: 18"L x 60"W 26"H
Stand Dimensions: 18" L x 60"W x 18"H

I know I would have to upgrade the lights which need to cover 60" instead as of now 48" or for the one 72" in case I choose 125G.

What do you guys think ?

I appreciate any advice.

Thanks