[fishnut]

Sorry for your loss.

I know how easy it is to forego regular testing when everything appears to be doing well.

However, I believe your parameters are a bit out of whack - the ammonia and nitrite, for instance - they should read zero, and nitrates are also somewhat high.

That is, if your test kit is accurate. IMO, it is best to keep and use up-to date test kits - in this way, trends and changes can be spotted (and noted in a log book) on a regular basis. The information supplied can be used to remedy problems before they become fatal (hopefully).

Or if an unforseen event does occur (as in this instance), the info about parameters can help to decipher why it happened.

Considering the cost of our livestock (and their replacement value, to say nothing of the emotional loss), test kits are worthwhile investments to protect them. Water is everything to fish, but we have no way of knowing how conducive it is to fish health unless we test it.

That said, the tank may have been a bit crowded, and regular large sized water changes would have been needed to keep up water quality, especially with messy eaters and defecators such as you had.

What kind of filtration do you have, and is maintenance done on a regular basis ? What size and type of skimmer ? Any changes in the last while ?
(Maintenance schedule, amount fed, livestock added ?)

I hope that you will look on these questions as just a way of trying to help you find answers - obviously you had success with this tank, since you had it for some years.

I wish you the best of luck in figuring out what went wrong, and hope that you will be able to learn something from this disaster that will enhance your future fishkeeping endeavors.