Rust?

okay i think i know the answer to this one before i even ask it ... my tank has been declining slowly when it comes to my fish loss of appitite not swimming as much ich outbreaks the whole works but corals are doing great. i woke up this morning to find that my orange spot goby went from looking great to dead almost unrecognizeable with black slime on him and my clown died and my engineer goby is nowhere to be found. so i did all the water tests and nothing bad all water levels good so i dug deeper and deeper found that my heater which is metal cased looks like its begun to rust for some reason is this the culpret or do i need to look somewhere else. any input would be good.

 

First and foremost, get rid of the rusty heater and anything else that is metal ie. thermometer!!!!!!!!!!!!!!!!!!!!!!!!!! Chemicals released by the rust pollute and often times can kill inverts and corals especially, fairly quickly as would copper.
I would do a water change, then add carbon to aid in removing the contaminants as a start.

 

yea heater is in the trash and did the water change and put in carbon..but the wierd thing is the corals are doing great i mean really great?

 

You know, I dont know where I've read that corals can thrive with rust. I dont know about inverts and fish, but corals seem to not mind it's presence. When they sink boats, what do you think all the metal parts become... rust.

You did good in removing the heater. I mean... c'mon making parts from metal for the fish hobby? It must have been old or for freshwater. Not meant for a coral reef.