HELP! Fish Seizure!?

[insecurity]

Here we go:
Type of Fish: Dwarf Puffer- probably nearing maturity. I was in the process of a water change, adding water & dechlorinator when I saw it happen. The puffer starting spazzing (twitching) uncontrollably then immediately sunk. I grabbed the net and nudged him. Gone. Not only did I pay a nice dollar for these fish, but me and my younger sister had grown quite attached to these miniscule cuties.
I checked the tank parameters with the API Master Test Kit. The results were:
ph: 6.8
High ph: Not Tested
Ammonia: close to 0ppm
Nitrite: 0ppm
Nitrate: close to 0ppm

The tank specs are as follows: Standard 20gal filtered with a Fluval U3. Setup in November 2012, and completely stablized by late December 2012.

Fellow tank mates were 2 other dwarf puffers and 3 otos. No other strange behaviour and symptoms.

Upon removal from the tank, I attempted to study the puffer for abnormal coloration and markings, but with the small nature of these guys, it proved next to impossible.

I think I answered almost everything from the checklist...

 

[oscarchic11]

im guessing that ur tank is fresh? dwarf puffers need brackish, and later full marine salt tanks 2 thrive. sorry for the loss! those guys are cute, but i never got one for that reason...

 

[Zippo1313]

Are u sure I know the green spotted and the figure 8 need to be brack then salt but I think I have read on here that dwarfs are fresh only

 

[insecurity]

These puffers are freshwater all about them here: Dwarf Puffers : Home

 

[insecurity]

Well, more bad news. Checked the tank this morning: all the other fish passed away.
So I sucked the tank dry and got rid of the live plants (sold them).

Anybody have any clue what might've happened? I've read about massive tank death before, but I was always under the impression it typically happened in less than 24 hours. In this case, it was closer to 48 hours.

I figured some sort of disease, so that's why I sucked it dry.

 

[Wiggles24]

It doesn't sound like a disease at all. The problrmd started right after a water change right?

 

[Oceangirl]

Did you add dechloranator then add water or add water and then dechlorinate?
You should have a little nitrates, were you heavily planted? Are you sure you added your prime? Change water conditioners? If they were maturing, are your sure they didn't need brackish water?

 

[insecurity]

Did you add dechloranator then add water or add water and then dechlorinate?
You should have a little nitrates, were you heavily planted? Are you sure you added your prime? Change water conditioners? If they were maturing, are your sure they didn't need brackish water?

I use the Aqueon Water Changer, so as its filling up I had added the dechlorinator.
I did have some nitrates- the color was reading in just a tad darker than 0ppm. That, and yes, it was heavily planted.
I had never used Prime, but I did use a similar product that I injected into the substrate.

Either way- whatever the cause, I'm assuming its gone, after I sucked it dry. I refilled it, cranked the heat, changed the times on the timer for the light and added some API Quick Start.

I'm leaving the tank be for a couple days, then I'll do a full panel water test, water change, etc.