You quoted this below,,,
"Ammonia due to over feeding: The could of been one reason, but without feeding the fish for a week; some fish came back to perfect condition for a period of 4-5 days, with no problems, which makes me question ammonia poisoning as what i have learnt is that it permanently effects the fish so, i don't see how they could be looking healthy again, chasing each other and basically looking 'cured'.
Additionally, i feel that ammonia poisoning would have more of an effect on clown loaches and my bristle nose's and Gold spot".
I'm just correcting you on this as your incorrect.
You said after not feeding for a week some fish come back to normal,,,, (this points fingers to ammonia being the problem).
You said ammonia permanently effects fish, in a fashion of saying it permanently effects fish in any level of exposure,,,,, well that's very wrong, because most fish can handle low levels, short exposure of ammonia while some others can handle a little more within reason.
You see, some of your fish were effected more than others due to different tolerance levels, being either species differences or just straight out some having better immune systems to each other.
I'll use a horrible example to explain better,,,,,, when Hilter gased the Jews in large cells of 100 people, about 15 would survive then they'd get put into the next gassing,,, sometimes all would die, sometimes one would survive.
You see there are so many reasons that determine probability,,, to take one observation and be black and white on a decision is not a scientific approach.
After your description of outcome after not feeding. (YOUR FISH WERE AMMONIA POISONED), Over feeding, over stocking, insufficient filtration, conditions not matured enough are always most common reasons,
I mean if the ammonia spike would of been the cause, i don't see how they could of gone from from, terrible condition to perfect, back to terrible. if the ammonia effects them permanently
After cleaning out the tank, and all the coral sand ~ i encountered heaps of medium - short red worms. I'm guessing this would of been the cause. They must of entered the tank via the introduction of the new plant.
Does anyone know how to quarantine the tank from these? before i re-start? thanks.