Hi, thanks for your replies.
I have contacted with the seller, and he confirmed his mistake and the compound MnSO4 monohydrate, so the Mn in water is actually 18
mg/l (I assumed wrongly it was tetrahydrated). I have found some papers where they state that the LC50 (lethal concentration in 96h) ranges 2-4 mg/l for surface waters' fishes in British Columbia, and around 5 mg/l, in a paper where it was tested with a cyprinidus fish (same family than goldfish)...
I have put some fishes in a temporary pond with new water, the rest of fishes escape to my net: tomorrow morning I'll empty the pond to catch the rest before it is too late. I hope they will not have sequels, please...
I'll refill with RO water + tap, it will take 3 days. The plants will suffer for sure.
Maybe I'll filter with cation exchange (H+ form) resin or mixed bed resin, the last 200 liters, instead of emptying totally. Or if not posible I'll empty completety the pond, and sorry if there are some very small fishes from last spring...
Ambient Water Quality Guidelines for Manganese
Comparative toxicity of eight metals on freshwater fish. - PubMed - NCBI
The fishes are now in a new clean water pool, with no manganese, but that has been between 24 and 36 hours after the overdose, I am worried about fishes health.
Please, do you know some medication/product to health or detoxify fishes when intoxication by heavy metals? Maybe there is something out there? Or maybe some of you has medicated some time fishes for this?
I have read some papers explaining the health improvement (even curation) of severe manganese intoxication, by applying sodium para-aminosalicylic acid, but this is for humans and I would not dare to try a thing like this blindly.
Do you know of some product or treatment, please?