Review on 🐠 HuYaYa 4 Pack Pre-Filter Sponge Rolls for Fish Tank Aquarium - Compatible Foam Pre-Filter Accessories for Filter System by Amber Jackson

TL;DR Moral of the story: if you buy these filters, don't over wash them. Don't think that a quick rinse is enough. ----------- I've been doing this hobby for almost 5 years now and have experimented with many devices. I have never had a product that nearly killed all of my fish. The fish began acting strangely almost immediately, some shaking violently and eventually sinking to the bottom and becoming lethargic. I removed the filter as soon as I saw the strange behavior. After 30 minutes I started an emergency water change and after another 20 minutes I put all my fish in the second tank when they started rolling on their sides. Luckily the transfer saved her, but it was almost a complete disaster. After cleaning the tank and adding fresh carbon to the filters, I put them back in, filled the tank and let it run for 24 hours. Then I put the lucky subject back in the aquarium and let him swim for another 24 hours. He survived so I put the rest of the fish back in the tank. They all appear to be healthy. Now that the filters are clean they catch a lot of crap well before it gets into my canister filters. I'm happy with that, but I'm giving this a final 2 star rating because nothing that gets into an aquarium should be that toxic. The moral of the story is, if you buy these filters, overflow them. Don't think that a quick rinse is enough.