Like many people who come to Purigen, it was after I decided to add mopani wood to my tank. I added a lot... a LOT of mopani wood to my 55 gallon tank. A beautiful build, but within a couple hours I could not see the back of the tank for all the tannins. Actually, barely 2 inches of visibility. Forget "tea-colored" water... I had a full tank of hot cocoa!

After much google-fu and other Amazon reviews here, I figured this might help. Oh...emmmm  geee! Within hours I could see the back of the tank and in a day the water was clear! I could see my critters again and they seem happier than ever with their clear water. Only negative (possibly) is that my Purigen has become colored to the point it should be "regenerated", so I burnt through it fast. Then again, I gave this tiny bag a tremendous task and it didn't fail.

Even though I could regenerate it, I am going to buy another bag since it is so cheap.

The bag is a perfect fit for any hang-on-the-back filter. All that empty space in the back of your filter is actually meant for add-ons such as this. Just push it in and it begins polishing immediately. I left in my carbon and floss since they have all the good bacteria and this product is only chemical purification. I don't think the bag and fine grains would do well as a mechanical and bio filter in my opinion, as the regeneration process would sterilize it.

tl;dr: Got mopani? This is what you need.
Like many people who come to Purigen, it was after I decided to add mopani wood to my tank. I added a lot... a LOT of mopani wood to my 55 gallon tank. A beautiful build, but within a couple hours I could not see the back of the tank for all the tannins. Actually, barely 2 inches of visibility. Forget "tea-colored" water... I had a full tank of hot cocoa! After much google-fu and other Amazon reviews here, I figured this might help. Oh... emmmm  geee! Within hours I could see the back of the tank and in a day the water was clear! I could see my critters again and they seem happier than ever with their clear water. Only negative (possibly) is that my Purigen has become colored to the point it should be "regenerated", so I burnt through it fast. Then again, I gave this tiny bag a tremendous task and it didn't fail. Even though I could regenerate it, I am going to buy another bag since it is so cheap. The bag is a perfect fit for any hang-on-the-back filter. All that empty space in the back of your filter is actually meant for add-ons such as this. Just push it in and it begins polishing immediately. I left in my carbon and floss since they have all the good bacteria and this product is only chemical purification. I don't think the bag and fine grains would do well as a mechanical and bio filter in my opinion, as the regeneration process would sterilize it. tl;dr: Got mopani? This is what you need.