I have always been rather sceptical about products that claim to boost your biological filter, in fact many people dismiss these products totally. However, I have to say that after using stress zyme on a small 20 gallon tank aquarium, I am now looking upon these products in a completely different light.

I set the aquarium up about five weeks ago and introduced two Cory catfish. I then followed the instructions on the stress zyme bottle, add 10 mills to every 10 US gallons. That worked out slightly less in the UK. I had to do this on the 1st 7th and 14th day. Intermittent water tests showed excellent results with no toxins present. I added six Cardinal tetras a week ago, unfortunately five of them died within a day, the last one is perfectly okay. I carried out a water test today, ammonia, nitrite and nitrate. Ammonia and nitrite 0, nitrate in between zero and five. So, we have to conclude that this product does work because I have done no water changes since setting the tank up and I have had no ammonia or nitrite readings at all. And we have nitrate reading which means that ammonia and nitrite are being dealt with by the bacteria.

I don't think you should let it go to your head, be very careful at this stage when adding more fish, add them very gradually or you might run into problems.

OFL, I would love to believe that these things work. I used Stress Zyme once. That cycle was on a 55 gal (US) that have a sponge filter and two 2in goldfish. That cycle took three months. Yes, three months. I also tried a product called TLC on my 125 when I set it up. That cycle was on two Emperor 400 filters stocked with one 5in Oscar. The cycle took about a month but upon completion I have a massive waterborne algae outbreak. That's the ONLY time I've ever had that happen indoors. Could there actually be LIVE bacteria kept in a bottle for long periods of time with at best a very finite food source? I personally doubt it.

I have a hunch that there are a heck of a lot more factors involved in the initial cycle than people are aware of. The best way of getting through one successfully is a heavy dose of patience.

This is interesting. I been wondering as well how the bacteria could stay alive for so long.
Don't know if we get Stress Zyme here but some similar products, and people say some work and some don't.

Thinking if it's really live bacteria, it can't be a great amount if you consider the surface of filter material and surfaces in the tank compared to what's in the package, but would be something to start with. Still they need some time to multiply, especially the ones breaking down nitrite, so if it works at all, it wouldn't be advisable anyway to fully stock a tank and expect zero toxins right after adding that stuff. And wouldn't work neither with no fish or at least some "waste" for bacteria food at all. Just what I think.

I used such a product only once yet in a small tank since it came with it, and i had very low nitrite readings (didn't have any ammonia at all when testing first time), and only for a short time. Might as well be that was because there were only few small fish in the tank, hard to tell.

I can only report results from what I have experienced. Did another water test two days ago, this was six weeks after adding the fish. No water changes as of yet. Ammonia and nitrite zero, nitrate 10. There is only three fish in there and they are only small. However, it is only a 20 gallon tank and I would expect have expected to see some kind of ammonia/nitrite readings if I had not used stress zyme. Maybe I will try and find somebody from the company to come on here and explain how it works. But like you, I am at a loss to understand how they can keep bacteria that neither surfaced to live on and also oxygen alive in a bottle.

Here in New Zealand the pet shops live by stress zyme every shop has a huge stress zyme dispenser and every fish that gets bagged for sale gets two squirts os stress zyme before getting handed over to customer,i suppose it must work for them do go this route,but as OFL said it would be nice to get someone from stress zyme on this forum to give us some facts on how this product acctualy works.

I am guessing there is some science behind it. Maybe the bacteria are in a kind of suspended state and opening the bottle and putting in water causes it to change and it starts working