Yes, plenty of salt creep evident. No matter what kind of power bar you use, metal/plastic/heavy duty, it won't hold up to moisture exposure & salt creep. Might be wise to think about how & where you have this power bar mounted.

Every receptacle is designed and CSA certified to handle the load that the NEMA configuration allows for. Meaning each receptacle in a common power bar can handle the full load of the power bar(even though many are protected by internal overcurrent devices).
Problem for reefers is that the salt environment causes corrosion on our plugs making resistance in the connections. This resistance(with current running through it) creates heat, more heat = more resistance = more heat continuing till something melts. Breakers usually don't trip because current draw is not high enough. Most 15A breakers will hold 20A for a while, old FPE stablock breakers will hold a dead short for waaayyy to long.
Cheap plastic power bars usually melt and let go of their connection before fire. I would be afraid that a metal power bar(being stronger) would just hold on longer and create more heat. Better solution is to clean your connections and use an anti-oxidising compound if it's really bad.

Hopefully helpful information
 

By code a 15 amp circuit is allowed a total of 1200 watts. So traditionally each 15 amp circuit has 12 outlets of lights & plugs rated for 100 watts at each outlet. Most of us that have aquariums use a power bar to operate the various things such as heaters, skimmers, lighting etc. When you plug a power bar into a wall outlet, remember to choose a wall plug in that's not on a circuit that's heavily loaded. So do the math and figure out your total wattage for your aquarium and what's on the other plugs in that circuit to try and keep it at 1200 watts maximum. For the sake of safety try and use at least 2 different circuits especially if your have high wattages such as MH lights & heaters. I also agree that your power bar should be mounted in the driest area possible to avoid salt creep causing you grief.
:attention:

You're correct that a 15A circuit is not allowed to be loaded up to 15A. Almost all breakers out there are only rated for 80% capacity, 100% rated breakers are rare(usually in large commercial and industrial where there is no space for a larger breaker frame size)
I forget if the 12 plugs per circuit is a code rule or just a rule of thumb, either way, 10 to 12 devices on a circuit is the norm. Each plug is still rated for the full load of the circuit though, not 100 watts. Just if you plug enough stuff in it will trip the breaker...

power bar melt
 

My power bar was not powering M/H, only had 4 - 96 watt compact florescent, 6 led moonlights, and 2 koralia power heads. Maybe 600 watts or 5 amps. It was only 2 months old and was kept in the dry area of cabinet. Not enough current draw for the coralife power bar to melt and cause a fire like it did. I would never recommend this power bar to anybody.

I typed up an amazing reply here and then my computer froze so... now you get this haha.

Cheap power bars are exactly that and you get what you pay for. With that said plugging 3 MH into any power bar is going to be a bad idea. Yes the outlet on the wall is rated to carry a 15A or 1800W load and so is the wire in the wall connected to it. The wiring inside the power bar is going to be significantly smaller than the wiring in your wall likely only rated to carry something between 5 and 10 amps depending on manufacturer and quality of power bar. Pretty easy to see how putting a few things into a power bar can quickly overload/overheat the power bar without ever causing an issue for the breaker protecting the circuit. The same is true for most readily available extension cords.

Our Tanks can very quickly become a very large electrical demand on the wiring in our homes. Ideally we would be able to run dedicated circuits to them but sometimes that doesn't happen. At the very least you should do your best to plug the higher draw items like MH lighting into higher end power blocks like you would see for home theater equipment as these often have the heavier gauge wiring in them to handle the draw. if you can't do this make sure you keep an eye on things.

In this particular situation I would agree the moisture and salt definitely accelerated the problem but it likely would have happened anyway. This is something I see on a regular basis (at least weekly) with my job. People always overload power bars. If possible we should keep as much of the electrical as isolated from the wet/damp environment as possible obviously without a sizeable fish room this can be pretty tricky.

Just a few other electrical safety thoughts.

If your house is more than 20 years old you should consider having your panel inspected by a qualified electrician who specializes in residential service (working on existing occupied homes) and very likely plan on replacing your breakers. Breakers have a 20-30yr life expectancy under ideal conditions, as they age and stop working properly they will not trip when they are supposed to and this can lead to some pretty serious fire risks in your home. The electrical in your home is just like anything else out there, it wears out over time and needs to be properly maintained to function properly and safely.

Okay I should stop now but just a quick word on GFCI's

Just because there is water close doesn't mean you need a GFCI. If there is a sink, bathtub or shower nearby then yes code says you need it. A fish tank does not require GFCI protection and while it is a good idea for some items I would recommend that items vital to tank survival like pumps and power heads not be GFCI protected as they may cause the GFCI to trip when not needed and if not caught can be disastrous to your system... just my personal opinion on the GFCI matter. Depending on how the burning took place a GFCI may or may not have prevented this melted power bar.

I find just the opposite, especially if a breaker has been tripped more than half a dozen times or so they tend to trip more easy, but yes breakers do wear out.

Yup repeated cycling will wear out the mechanisms resulting in tripping early... frustrating, but safe.

The safety issues come from age related issues with the metal components like good old corrosion. Additionally the changing flow of power over the years heats and cools the metals and they can start to fuse together over time. And if your lucky enough to have a Federal Pacific/Pioneer stab lock panel breakers probably didn't trip when they were supposed to from day one so now in extreme cases the internals could be full on welded together :surprise: Surprisingly reliable check, turn your breakers off then back on, if the handles don't move smoothly and easily there is probably some internal corrosion going on and may be time to replace.

Side note... If you have a Federal Pacific, Federal Pioneer, Sylvania, or CEB panel, call an electrician and get it out of your house they all have known issues with their breakers not tripping when they are supposed to.

okay I'm going to try to stop preaching electrical safety now haha.

Not certain about code requirements with regard to GFCI & fish tanks, but if it is code to have one near sinks, bathtubs etc., doesn't it make sense to use a GFCI for equipment powering a fish tank full of water? Especially if you're going to be reaching body parts into it from time to time? Code, schmode & if my critters die due to a GFCI tripping, I'd sooner deal with that, than risking my own or my family's skin.

holy frak! Glad you didn't burn your house down Tai! Had to go check my cheap powerbars, then remembered that I have my all my lights plugged into one GHL profilux powerbar which was anything but cheap..