Did rust cause my system to "tank"?

[marineboy0]

After my fish and live rock system progressively died off due to what I think was a progressive water chemistry failure. I finally decided to pull it apart to try and find the cause. Salinity, KH, pH, NH3, NO3, PO4

Almost immediately, I found a 2"x5" stainless gauze, that had been originally put in to screen the inlet of one of the sump pumps, resting in the bottom. The stainless had started to badly oxidize. Would this have been sufficient to cause a cumulative toxic effect ? Is there a water test for ferric and /or ferrous oxide and what would be consider toxic?

Would it be possible to recover all the substrate and live rock and rebuild the system. Or should I dispose of the substrate and start over? I hope to recover the rock and reuse that. I'm leaning towards replacing the substrate as I used copper medication as a last ditch misguided hope to save the fish.

I wish to set the system back up again for fish only. Would you advise not to bother with the plenum?

SETUP:
Water chemistry before being taken apart : Salinity SG1021 , KH 130, pH 8.2, NH3 <0.1, NO3 0.1, PO4 0.25.
The system details are two display tanks of 30g and 55g with separate pumps from a 80g plenum sump with 150lb calcium argonite, 6'x4" DIY protein skimmer and 32gallon plastic trash can with polystrene peanuts as trickle filter. Inline activated carbon and chemical phosphate removal canisters.

 

[Randy Holmes-Farley]

The iron would not be a problem, but other metals in the stainless might possibly have been a problem. Not likely, but possible.

You can test for iron, but I add iron and recommend that others that grow macroalgae do so as well. never has it appeared to lead to a tank crash that I know of.

The fish died too? Over what period of time?

I'd try to figure out what happened before deciding to reuse live rock.

 

[marineboy0]

The fish died over a 3 week period in the sequence of fire shrimp then flame angle, clown fish, naso tang, copper butterfly,(added copper medication at this point) diane wrasse and lastly puffer fish.

If not the iron oxide then I'll keep pulling the system apart. My other two concerns were copper or aluminium from heating coils and also eleachables from the expanded polystyrene. But I might be on completely the wrong thought process - except thta about 2 weeks ago I introduced 3 green chromis and with 6 hours all three were dead - threefore I have concluded that there is a highly toxic element to the system. Any thoughts?

 

[Randy Holmes-Farley]

Had those other fish been in the tank for a long time before that?

Do you use tap water?