Few Questions - Need Some Help/Opinions

[thutton33]

Hello,
Well the worst thing possible happened this morning, Woke up to an entirely dead community (5 Angels, 3 Silver Dollars). I need some help with finding out what could have happened first of all.

Some Facts:
The Wife's Tank Still has some fish so the water used in water change may not be the cause (My tank is 75g and hers is 10g so there could be "Some" of the problem in her tank but not as much as mine and hence the difference)

I have not added fish in at least 6 months

I HAVE added java moss about a week ago and this is the first bad thing to happen, If it was the moss I would have expected it earlier

It was a very aged tank I have had it over 4 years

Waking up to the dead fish today BUT the moss was perfectly healthy no signs of withering or dying

The fish only showed a slight bit of cloud eye the night before the incident, I added Malefix (Directions we followed on dosage)

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Question 2

What do I need to do to make sure that the cause is removed before re-stocking.

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Question 3

Please give some suggestions on the "population" to restock it with (I would Like some Angels, so lets try to keep it as Friendly as possible)

[MCluett]

how did you acclimatize the fish? what are your parameters? i am a SW guy but people will need to know this info to help you out. also before restocking you should do a large PWC and definatly find out what the problem is first.

[thutton33]

Yes all the fish were properly acclimated as there have been there from 6 Months to 3 Years.

the water has been stable for years... I dont remember the stats 100% but it was PH of mid to high 6's constant temp of 30, Good filtration (Fluval 404)

[MCluett]

ok i think most people will still want to know the ammonia, nitrite, and nitrate levels. would you be able to test them anytime soon?

[thutton33]

Yes I am running my full panel when I arrive home from work today, if I did have an ammonia spike (somhow) what would the symptoms be (IE how would the fish look once they die, characteristics) and would my Moss still be perfectly heathly?

[saffikeagan]

Who did the PWC on each of the tanks? Maybe something like hand lotion or soap on one set of hands not present on another.

[MCluett]

i dont what the fish would look like after but were any of the fish laboring to breath prior to there death? i know that is a sign of high ammonia

[thutton33]

as a matter of fact I think I did see laboured breating from my silver dollars and the angels (for the most part) were staying at the top, on my way to bed last night....

Wow would ammonia get in there? and would it not effect the moss? there was no lotion or anything like that it was myself that did the change (note the change was a few nights before this happend)

I do also use the water solution prior to the water going into the tank

[MCluett]

chemicals are not recommended if they are not needed. if it was ammonia it could have been caused by over feeding, or if you cleaned the filter to much removing the needed bacteria, which may have caused a mini cycle. check your ammonia when you get home to know for sure

[An t-iasg]

Some possibilities:
As already mentioned - did you remove too much filter media during a filter cleaning? Media like sponges and ceramic rings should only be rinsed gently in removed tank water, and this isn't necessary every week. You can replace filter floss once a week. Did you do a major redecoration or rearraging of the tank and stir up the substrate, possibly releasing a lot of rotting material that the biological filter can't handle right away? These situations could lead to an ammonia spike.

Is there any possibility that your heater malfunctioned?

Were the gills red? You mentioned labored breathing. That could be related to an ammonia spike or possibly a bacterial infection. Cloudy eyes are often an indicator of poor water quality. Is there any possibility that your tapwater source has changed? When was the last time you did a water change? Are they done regularly - once a week? Could you have possibly forgotten the dechlorinator?