Fish Dying, Bad Day...

Came home today and my last adult male guppy (The best one and my favorite) is missing from the tank. I removed driftwood, went through plants etc. Can't find him anywhere, shut down my new fluval 204 to my 20 gallon tank, looked in it. No idea what happened to him.

Do ADF's eat fish? I mean can they? Maybe if the fish is dead?
I know I do NOT have clawed frogs they are ADF's...or maybe it is the Ghost shrimp and Mystery Snails that ate him? They sure did it fast cause he was just there earlier today...

I added some Flourish trace, and some excel since I am leaving for the weekend. a few minutes later I notice one of my oto's laying upside down on the tank bottem. He is alive and looks normal but he cannot swim, when the tries he just kinda turns in a circle untill he gives up and sinks to the bottom.

He was fine for a few minues after this swimming with the other otto, then suddenly circles again and laying on bottom.

Looks like I might be missing a few guppy fry too, I knwo I put more in there than I have now...

I feel like im an @ss for killing all my fish but I don't know why they are dying. The only thing I added recently was flourish trace, and the new filter. So what is killing my fish Amonia & Nitirtes both dropped to once I installed the Fluval 204. The old whisper 10i is of course still in the tank too.

well that explains the fish disappearing, but now to figure out why they are dying?

Could it be from the new Fluval 204? too much current? Or maybe from dosing Flourish Trace? (it says copper in its ingreadiants so I'm kinda skeptical on continuing it's use)

So I got home and the oto was dead and the snails had eaten his brains!

I removed the dead fish and tested the water.

0 Nitrite
0 amonia
PH 7.2

Did not test Nitrate (but I can never keep it high enough usualy around 5ppm or less)

I noticed one of the bumblee bee gobies was not looking too well so I did a 25% water change, and added aquarium salt (rather than using prime this time around). 1 TSB per 5 gallons. I also flushed the fluval filter water (water inside the filter) because it looked icky and was easy to do. Bumble Bee gobies seem happier with minimal aquarium salt added (at least the healthier one did), and other fish and snails seem unaffected.

Will report back tomarrow when I get home from work.

everything I listed is what I have. I dosed the trace acording to directions.

I doesed the salt but not heavily 1 TSB per 5 gallons. I will add some Pimafix in there when I get home. It looks as though the Gobies Fins are rotting, but very slowly so I think it might just be the cause of stress. not sure what from though...

Don't know why the Otto died, or the guppy, they were fine one day and dead the next. All the other guppys look healthy.

Thank is medium planted. but it's fiarly new so definately not Heavily planted yet.

Ok, I will do another water cange when I get home to almost eliminate the salt compleatly. Then I will remove charcoal and add Pimafix instead.

I was told he amount of salt I am adding would not bother my snails at all, because it was a concern of mine. I have about 30-40 in there right now growing up fast!