Re: Microelements Excess CU
dkarmona said:
Usually fish last a long time in my aquariums but recently (month or maybe two) I am in a down spirall, I am managing to have "happy" plants, I didn't introduce new fish, since they don't die, no new fish. I haven't seen ich in a very long time, but two platties, a big blue gourami and a pelvicachromis pulcher died in the last month or two. None had any sign of disease the gourami appeared one day death, the same with the pulcher and the platties just dissapeared. From a recent post in the mailing list I was thinking of this
There is no real set and forget substrate over the longer term
My substrate is commond sand (2mm aprox), one year old, never cleaned, with a 2 mm layer of peat (no handfull). So many things to consider, now I am doing better with the plants not better with the fish, and brown dust has began to appear, this gets complicated, when you think you have one thing under control something else pops up.

And finally my shrimp disssapeared.
I think now you are the right track Diego.
Here's what you can do and some of the potentail issues you might have.
H2S is possible, other gases from an old substrate, you likely have TOO MUCH organic matter, peat + too much mulm in there.
What this does is reduces the substrate much firther than is ideal.
Then you get nasty things like H2S, and reduction of Al and other metals.
This also reduces O2 levels.
How to solve things:
I'd suggest vacuuming with a gravel vac in 1/4 sections, uproot the plants in the section, vacuum all the way to the bottom, remove everything.
Replant, do at least 50-60% water changes.
Wait 3-7 days, do the next section till you have finished the tank.
Now you can re slope the gravel how you would like it, replant something different, plants will also grow better now, more O2, cleaner, healthier fish and plants.
I did find some older references that suggested Zebra danios are the most senstive to copper and then live bearers etc on down to cichlids.
But I think that is not the case here.
After cleaning the gravel you switch to a plant specidfic type of substrate if you wish, the reduction and the vacuuming/repolanting/uprooting is still needed every so often though.
Mulm is good in the beginning to help start up a tank, too much adds too much breduction and that harms the tank, not helps, so yes, there is no set and forget substrate, it needs maintaneance as well.
I like uprooting at least once a month for most plants, Crypts, Crinums and few others I will leave that have awesome roots systems loaded with aerenchyma, that helps cycle the mulm and break it down by pumping the O2 deep into the gravel.
Many plants are not good at that. Simply because these plants do this, does not imply they prefer root feeding.
You can add SEaChem tabs back to the gravel once you get it all cleaned up.
Given the wide range of fish dying, I do not think it's Cu.
One sensitive species perhaps..........but you are losing more than one species and not really dosing more than anyone else that's not losing fish.
So I think you can rule that one out.
Try the gravel cleaning, you are due for it anyway.
You can always try out some Zebra danios for a Cu test
Regards,
Tom Barr