If your pond seems to be out of balance or if your animals show worrying behaviour or die, this could be a result of poisoning, even if the water tests aren’t indicating the wrong water levels.
Here is an outline of possible poisonings and remedial measures. It is essential that you react as quickly as possible!
Further ways to destroy the beneficial bacteria in the pond
If you have added salt to your pond (why? This does more harm than good), your bacteria won’t like that at all. Bacteria can’t get used to fluctuating salinity. If you insist on adding salt, you will have to restart the bacterial fauna AFTER the adding of salt with JBL FilterStart Pond and JBL BactoPond .
Neither do your bacteria like you adding antibacterial medicines to your pond because the medicines can’t differentiate between beneficial cleansing bacteria and pathogenic bacteria. Also in this case a bacterial reactivation with JBL FilterStart Pond and JBL BactoPond is urgently advised.