I have come across a few concerns also,
but most can be avoided if you do proper maintenance
the biggest issue I found was the 3 fans , they draw in lots of airborne particles such as dust
and over time it builds up inside the unit , dust and electronics is a big concern with fire .
as long as this is done before you turn on lights use a can of compressed air to blow out any dust build up just be sure you cover the top of your tank so all the crud don't fall in ,
I do this once a week I also live on a dirt road so I get a lot of dust .
salt buildup is not a issue as I wipe my fixture down daily my light also sits 22inches above the water , the closer to water the build up gets worse , radio shack sells a spray that you can spray all the internal electronics that will help keep all connections from corroding , but like everything it's up to you to keep it clean ,
I found the dimmer switches to fail from always switching on and off so to avoid that don't switch light on from that switch just use that as the dimmer , there is a second on/off switch that can be used there is one for whites and one for blue , these switches seem to be more reliable IMO
as for rust I don't have that issue as I dismantled my light when I got it , and sprayed a clear appliance epoxy over the entire metal casing inside and out .
other than those small flaws I love my Chinese leds
my leds are the no name s
almost a year old
proper maintenance can help avoid some of the issues
for the cheap price nothings going to be perfect (switches can be replaced)