The compound magnesium iodide is a strong electrolyte write the reaction when solid magnesium iodide is put into water

  The  reaction  for magnesium  iodide  when put into water  is  as below

 MgI2(s) →  Mg^2+(aq)   + 2I^-(aq)

when  magnesium iodide  but into water it dissociate/ ionize  completely  into  Mg^2+  and  2l^-   ions. Magnesium iodide dissociate/ionize  completely because  magnesium  iodide  is a strong electrolyte  which  dissociate/ ionize  completely into their ions  when it is put into   water .

I’d have to say no because without oxygen in the water the fish would all be dead. so if you want to fish for dead fish, pick the ponds with the lowest oxygen concentrations.