Minnow Troubles: Tale of the vanishing fish

[Amphibianite]

So about two weeks ago I bought some White Cloud Minnows 12 to be exact. I set them up in the bare bottom, heavily planted, sponge filtered tank I was setting up for breeding betta. There is a number of plants and 3 mystery snails as well. There is an adjustable heater set at 70 and an ambiant air temp of 70-74 in the room thanks to a ceramic heater used to keep my bettas warms (Yes it works quite well many of the bettas are high 70s to 80 and the rest are mid 70s)

Now here comes the odd part of this all. At the end of the first week I have about 8 minnows that I could see on a regular basis. I figured the rest were hiding in the plants, as I could only hope for. Seems I was wrong over the course of the rest of the time till now the number has dwindled and fallen till it has come to only 2. The last two are in a new 5 gallon with 2 new mystery snails, and 3 less than inch currently albino cory cats. It is filtered. Currently ambient heated till new heater is set up.
(I am well aware the corys can not live in the tank long term)

So my question is what could be happening to my minnows?
Water temp is spot on for them, heavily planted, the snails are just fine(meaning not sick still very active)

Here is the history of the tank that I posted elsewhere before

"It used to hold toads, yes I know toxins, BUT it was unused for close to 6 months, then soaped, rinsed, bleached, rinsed, AQ salted soak and rinsed , and sat for for awhile then rinsed really really well again."

So does anyone have any ideas?

I am personally hoping it is something that is effecting only the minnows, because I personally do not want to have to restart my whole breeding tank. If I need to of course I will, I will not out my bettas or fry in danger.

[Oldfishlady]

How odd....the only thing I can think of is that they either jumped out or died and the snails ate them before you seen the bodies

Fish decomp really fast and snails can devour them pretty fast too......did the tank have a solid lid/cover.....

I love the white clouds one of the prettier cool water species.... too bad you lost most of them, hopefully the remaining 2 will be a breeding pair or a gravid female at least and you will have a nice school in no time....

[Amphibianite]

OFL - It has a fine mesh lid on it also the lid is a foot or so above the current water line so jumping out is nigh impossible.
I figured they died some how and the snails ate them, the question I am pondering is how did they die. Is it something I need to worry about, or can I continue my plan to use the tank and current water for my betta breeding tank.
The only thing I am waiting on to breed them is to finish conditioning and to get my worm cultures going full speed.

As for the white clouds breeding, I don't know if they can yet they are still extremely small. Less than half an inch at this point. I am planning on picking up another 12 or so today to give myself better chances at breeding them, as well as do the right thing and make sure they have a school.

[Oldfishlady]

Okay....I understand what you are talking about....and boy-O-boy......sometimes toxins can never be removed......that can be a mess...honestly I don't know much about the toads in question toxins-but generally toxins can be absorbed in the seals of glass tanks and if its acrylic-that can be worse.....the tank may never be safe for fish....but since the snails didn't die and you had the corydoras in that tank too....right?....and they didn't die.....so maybe it was just something wrong with the white clouds......since they are a cool water species it could have been too warm of water....or just a disease that was not related to the tank at all.....really hard to say since they didn't show or you didn't see any signs/symptoms before death.

What I would do.....if you have any other species of fish that are healthy-add them to the tank and see what happens....just one species of fish-no snails or anything.....

Did you by chance do a vinegar rinse on the tank-this may or may not help with toxins but it will cut any soap residue-but generally a small amount of soap residue will not kill fish anyway.....

Good luck.....

[Amphibianite]

The corys are in a 5 gal, not the 15-18 breeding tank.
Its a glass tank not an acrylic.
The snails are perfectly fine yes.
I have the water abut 70-72 degrees currently in that tank. I am hoping it is just a disease that came with the white clouds. I didn't see any symptoms no, they just started vanishing. The acted perfectly healthy, the two I have left seem happy and healthy.

The only fish I have currently is a community tank of gouramis and cory cats.
1 tetra tank with 4 tetras atm.
then my bettas.

I didn't do a vinegar rinse. What I did was wash it out really well with hot water. Then I filled it with water and a little bit of bleach let it sit for a few hours. Drained it, rinsed it really well. Then again filled it with hot water and AQ salt, let it sit for a few hours. Rinsed it really well. Then let it sit for awhile, rinsed it again in very hot water, and then added the water for the tank.
The plants are doing fine, the snails are perfectly healthy.

I am going today to the LFS to buy more White Clouds and put them in the new 5 gal set up to see how the act. See if it was the tank, or them. The best I could do is buy some other cheap fish and add them to the breeder tank to see what happens. I don't want to be cruel to fish though if it is a toxin problem.