This product cycled my tank (15 gallon Fluval Flex) in ...
356733
This product cycled my tank (15 gallon Fluval Flex) in nine days.  Make sure that you watch both fishless cycling videos from Dr. Tim.  I was stuck on a nitrite spike, with ammonia remaining, until I did a water change to bring the nitrite back down.  My tank processed the rest of the ammonia and nitrate within two days of the water change.
3290867
This is by far the most effective aquarium additive I have ever used. It's speeds up the cycle and significantly reduces the frequency of water changes ... without polluting the water with chemicals. I still test my water regularly - just less water changes. There's really no need to add anything else. Highly recommend.
2749888
I purchased this item as it states it can be used with fish that will be consumed by humans, not a claim most products can make.
I've used it to remove the Ammonia in my tanks when coming back from vacation (the ammonia built up while I was away)... and it worked! Will buy again!

Thanks Ecological Labs - I've blogged about this product too as I am so happy with it.
1019282
I did not buy this product from amazon, I bought it from a different source. This product is awesome. My planted tank surface was full of thick oil and bubbles. Removed everything is less than 60 minutes and I had the setting run at 50%.

Must have product for surface skimming.
4458759
This product has been great. I am using it to get my aquaponic system up and running. Fishless cycling. Not as exciting as having fish in there i must admit but i do enjoy the science of it all.
3550340
I have two 150 gallon aquariums.  The Rena Filstar XP4 filter in my bedroom aquarium quit working about 3 months ago.  I put one of the side mounted Marineland filters rated for 80 gallon tanks on it to help with the bioload until I could come up with a better solution.  It died for unknown reasons about 2 weeks ago.  Being a large African cichlid tank with huge plecos and Sydontus cats, the water turned nasty almost instantly.

I'd never tried a Penn Plax product, but decided to give this filter a try.  It arrived in about 3 days (well before it was estimated to arrive) and set up easily.  It ran overnight and my water was almost crystal clear the following morning.  I use the large water output option and actually have that piece underwater.  I can't even hear it running in my room, which is a HUGE improvement from the endless waterfall and buzzing I had previously.

I really hope this filter keeps working this well since I just ordered a second one for the living room tank.
4232689
I have been looking all over for straight ammonia.  All the store options have detergents. This simplified things!
I wanted a humane way to speed up the cycling of my tank and this worked perfectly. Thank you!
4851150
I love fluval but this doesn't work well at all on low water movement tanks... If you have pumps moving lots of water it holds pretty well... But not on my planted aquarium.. Killed two fish because it overheated the tank...
2705749
This really works! It helps me cycle a new tank and definitely helps the fish adjust and stay healthy. I wouldn't start a new tank without it.
1198278
So my CO2 system malfunctioned about 2 months ago and gassed my tank. I was lucky to catch it in time and I saved all my fish but since then I struggled to get the tank balanced again. I really did not want to use chemicals and have the tank become reliant on them however after a crazy alien algae attack took over my tank I decided I would try it.  I did lose many plants due to the water parameters going crazy however since I started using this product 2 weeks ago I am seeing a lot of new growth not covered in algae.  I went through my tank and removed most of my plants in hopes this product maintains balance from here on out and my new growth takes off to fill in the bare spots.
1923027
I purchased this and the Fluval Co2 diffuser at the same time, I received the Fluval diffuser a couple days prior to this product.

I hooked up my Fluval diffuser & after ONE day the product stopped working???  I'm running a DIY system so I just assumed that I needed more pressure.

I created another BIGGER dispensor in hopes of getting the Fluval working again but it never started up again.

A day later I received this in the mail, and hooked it up immediately within 2 minutes this product was working like a gem.  The bubbles aren't as fine as the fluval however the content that is coming out is diffusing before it's reaching the surface.

This product looks a 100 times better than the black disc Fluval is selling.  I apologize for bashing Fluval but this product was 1/2 the cost and actually WORKS.
1976421
I really like and have had sucess getting my 10 - 20 gallon tanks cycled faster with the "original" Tetra Safe Start - 3.38 oz bottle. Although have never tried Safe Start Plus+, which is most likely better. I've just used it for years so doing "fish-in cycling" and "fishless cycling". Occasionally you will get a "dud" bottle. Mostl likely because it got too hot during transit, but 90% of the time the bacteria is alive and ready to get to work on ammonia and nitrites. It introduces bacteria that immediately starts working. In my past experiences you see changes in nitrates within a  few days, often never seeing the nitrites ever go past 0ppm and the ammonia falls off there after to 0ppm. I have used Seachem Stability, as well as API Quick Start and both are also great producrts, but the Tetra Safe Start seems to get the tank cycled a bit faster. Possibly cutting a week or two off the cycling process. Great Product!
2382512
I have 11 freshwater aquariums varying in size from 5 gallons to 120 gallons.  I have used Prime, and other water treatments.  I wanted to wait to see how this product did with all of my fish.  It works very well.  I see no difference in this and Prime with the very important exception that it is completely odorless.
2836543
I use this is in my freshwater tank because I have driftwood in it and don't like the color of the water with the tannins.  Within 24 hours it made my water look amazing, bright and WHITE if that makes sense.  I did try to "recharge" the Purigen but could never get it back to the colorless stage like it was when it was brand new.  I followed all of the directions to a tee.  I put it back in my tank and over the course of the next five days I had 5 fish die :( I won't blame it on the Purigen because I did add two new fish around the same time so it's possible one of them introduced something nefarious into my tank - however, I won't take a chance with recharging it again I will just use a new packet of Purigen.  I have already ordered more and will continue to use because it is slightly costly but it makes a world of difference in the beauty of my aquarium which makes it worth it to me.
4819512
I was sick of adding tons of chemicals to my water every time my fish got sick - and when I first established the tank, it was often. So when I began to get worried if their stringy poop was because of parasites or the brine shrimp I was feeding them, and one fish was getting a film over his eyes, I bought this. His eyes cleared up and the fish got solid, dark colored poo so I was pleased to know it was a food issue, not parasites. I would have kept using this product except that it polluted the crap outta my water (definitely had to siphon more on weekly water changes) and the water was SO cloudy and yucky that I quit using the product. It didn't affect the levels (nitrates, nitrites, etc) but the tank was an embarrassment. Also, I can't say that my fish LOVED it like other people said their fish did. They actually like their cheap flakes more. I love the concept of this product and probably would have kept using it but for the thick fog it gave my tank. If people had come over and seen the tank- they would think I never cleaned the darn thing it was that bad. (and I do clean it once a week, FYI)
4977361
It's not overnight.  Took 3 weeks to cycle my tank.  Saltwater, Dry Rock, no fish.  I do believe using this product cut the time in half.
3795350
This stuff is awesome.  My 29 gallon tropical tank was very cloudy. I  vacuumed it and it was still very cloudy. The next day I replaced the charcoal in my aquaclear 70 with purichem. Within minutes I noticed that the water in the filter was like glass.  I  went to work and came back around 6 hours later.  My tank looked amazing.  It was almost like there was no water in the tank and my fish were floating.  The water was that clear.  3 days later the water is looking the same way.  I will definitely keep some purichem on hand now.  Great product.