Pleco fry dying - need some help please

[vanillarum]

I have a 40 gallon breeder tank that originally held my L046 colony. I moved the L046s out a while ago, and added 7 purple danios and 2 cory atropersonata to the barebottom tank. They have been fine for a coupla months. A month ago, I added some L400 fry (1 1/2" or bigger) to the tank from their breeding tank. All were dead in 2 days. I then took out the PP danios, and yesterday I added 4 red BN fry (1 1/2" again). Today - all dead. Corys are fine, swimming around like mad. There is an AC 70 and a sponge filter in/on the tank, as well as a Koralia water pump and an Aquaball 1212 air pump. The tank is bare bottom. Any suggestions ? I want to add another colony of plecos to the tank, and I am wondering if I should drain the tank, throw out the filter media, scrub everything and start again. I would add aan HOB from another tank that is already running. Thanx for any help.

[.Plecomania.]

if the tank is properly cycled and mature then i would think it had to do with water parameter differences. everything should be the same between this new tank and the old tank where the plecos will be transferred from.

[plecoboy]

Is there a sand substrate in the tank the L400 fry came from? I'm thinking they had a pH shock to the new tank which probably has a lower pH.

[ClearSky57]

Assuming your temps were similar...
Just a thought,,, but is the tank grounded... I have heard of younger fish getting zapersped by low current, when it doesn't appear to effect others..... maybe a bad heater or one of the powerheads????
you never know.... might not be enough to feel it yourself....

[vanillarum]

all the tanks are BB. Wouldn't an electrical shock have an effect on the cories ? And yikes, how the hang would I check that ? Thanx. Temps are the same.

[Supercorygirl]

Just a thought, as I've never bred plecos just corys, but before moving the fry over, drain the new tank and fill with water from the breeding tank. I lost a lot of fry from Cory's till I started doing this. Then with the water changes should acclimitze them to the different parameters between the 2 tanks. Hope it helps.

[vanillarum]

Draining 1 tank to the other is a great idea. And easy, too, as they are side by side. Thanx, I'll give it a shot.

[ClearSky57]

all the tanks are BB. Wouldn't an electrical shock have an effect on the cories ? And yikes, how the hang would I check that ? Thanx. Temps are the same.

If you had a low voltage issue, you wouldn't necessarily notice it, but it can react on some fish and not others... as i said, younger ones may be less tolerant. I'ts just a thought....
On my larger tanks or tanks with real costly fish in them, or if you have a system, it is simply a $10 ground fault plug in with a small probe that goes into the tank/system.

I bought 2 dozen young fish from a breeder in the midwest and acclimated them to my tanks/water the same way I've done with all my new arrivals, including L-046's, and a few fish even a bit higher priced, and I lost the entire bunch, one or two at a time. Other than nitrites a bit higher than normal, no other explanation for me..
I think sometimes we can have a "sour" tank that just doesn't cycle right or has bad karma?????
When I get one like that, (lost about 20 corys in one until I gave up) I just tear it down, and start over....

what kind of filtration did you say you had in yours???