It leaves a white scum on the water when mixed ...
932650
It leaves a white scum on the water when mixed, Don't know if this plugs up the filer but it's not very attractive.  Have no way to judge how effective it is??
2967689
Some kind of white surface material is flaking off inside my kettle. I'm going to replace it, since I don t know what it is and I'm surely drinking it.
2342651
I bought this to cycle my new nano 4.1 gallon tank. I read the instructions thoroughly and used it exactly as directed, but now I have a thick layer of white mucous-like film growing all over my filter to the point of not even being able to see the black part of the sponge. It's all over my plants as well and seems to be causing a lot of stress to my fish. It's been nearly 24 hours since I've poured it in and things only seem to be getting worse.
2699374
I have used this product for years.  In the past rinsing the muck off and re-using.  With my latest purchase, the white coarse filter disintegrated upon rinsing.  I will be ordering from another producer.
4316936
This will eventually deteriorate and put white flakey stuff in your water.  Not great.  Buy the Camco blue hoses.
311290
The water filters through slowly so that the coffee grounds float and back up into the water reservoir. The whole insides are covered with coffee grounds. Clean up becomes awful. I've thrown it away.
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.
2117660
***Algae-Off not only kills algae but it also floats leaves, fish waste and debris off the bottom of the pond so you can skim it all off.  It makes draining of the pond every spring to clean it a thing of the past.  It is safe for the fish unlike some other algae removers and very economical as a 25lb pail will last all summer, even with a bigger pond.***<------  This was my old review.  I ordered a new 25lb tub and they have changed the formula.  It no longer contains 85% of the active product.  It has been reduced to 50%.  It no longer floats leaves or small debris to the top nor lets me skim via backwash the green coating of lighter algae that covers the bottom.  I had part of an old 85% tub left and did half with old and half with new.  The old floated about a dozen leaves up and lots of green crud.  The new only showed the oxidation of the product with a white layer on the top like it looks when you use the old when the pond is clean.  I am very disappointed.  :(
1394848
I purchased because it does not eat away the cement stairs. However, it melts the top and then the melted water refreezes!
After all the ice has melted from the weather warming up, there is a messy residue left similar to flour mixed in water which gets tracked in on the shoes.
2 stars for refreezing of melted water and messy white residue.
4077647
The main reason I bought this citric acid was to clean the stains in the toilet tank reservoir.  I added the fine white powder into the tank and, a while later the discoloration on the inside surface of the tank was almost all gone.  I also used the powder to clean the washing machine but any cleaning results there were not so visible, the drum has a dark blue surface.  In using the powder on the bathtub, I found out that whenthe citric acid powder fries, it forms hard clumps on the surface.  These clumps wash away but now I know, don't let the citric acid powder dry.  This stuff is a whiz at cleaning toilet tanks.
740151
I live in San Francisco,  where hard water is a problem.  As a scientist, I'll tell you that the dissolved minerals, mostly calcium and magnesium bicarbonates, as well as sulfates, interfere with the chemical processes that are involved in detergents, such as body soaps, shampoo, dishwashing soap, and laundry soap.  This results in a scrub-resistant, sticky soap scum that clogs pores, gums up shower walls, clogs pipes, and deposits itself on clothing fibers.

This shower head is a little confusing to me.  Normal water softeners work by exchanging the calcium and magnesium ions with harmless sodium ions.  The product description mentions that the unit uses calcium sulfate (CaSO4), which is gypsum.  But calcium sulfate is typically *one of the things you want to remove* from hard water!  It's a major component of hard scale deposits.  In fact, when your water is too soft, the way to add hardness is to add calcium sulfate.

And I don't see any mention of sodium carbonate (Na2CO3), which you'd then need, leaving you with calcium carbonate (CaCO3) and sodium sulfate (NaSO4).  I'd love to hear from the manufacturer with more technical detail on *exactly* what ions are being removed, because the product description just says "Removes chlorine and other toxins."  I'm just not sure that really qualifies as water softening.  Also....what "toxins?"  That word gets overused a lot.

The other problem is that the unit does not come with any instructions, either for assembly or maintenance.  For example, there is no mention of how long the unit's lifespan is.  From a chemistry standpoint, whatever ion exchange is actually happening, can't happen forever.

Finally, LET ME MAKE LIFE EASIER FOR YOU!..... There are FIVE pieces: plastic shower head, silver ball joint, silver collar, black filter disc, white O-ring. Here's the order in which to assemble everything:
1.  Hold plastic shower head in one hand
2.  Add white O-ring to the neck of the shower head
3.  Balance silver ball joint on the white O-ring (ball side touching the ring)
4.  Screw silver collar onto the plastic shower head, which is what holds the ball joint in place.  Don't over-tighten because you won't be able to swivel the head.
5.  Insert black filter disc into the open, threaded side of the ball joint thing.
6.  Screw the threaded side to your shower pipe.

Why wasn't this printed anywhere?  I've included a few photos of the components and the unit fully assembled below.  I also want to note that the shower head causes an annoying howling sound, and I'm not enough of a plumber to figure out which piece is resonating.  I'll try tightening the shower head to the pipe further, or see if removing the O-ring does something.  Maybe that'll change the pressure situation, and therefore stop the howling.

Bottom line: I'm puzzled about the science of what's happening, specifically related to the technical process of water softening.  I'd love to see more information, and since there isn't any included in the package, it makes it hard to truly evaluate this product as a "water softener."  As a shower filter, it's a different story, but those two things are not equivalent.  And they should really include instructions---it would save aggravation.

---Sale price accepted on this item in exchange for a candid review.---
1094586
First off, this aquarium decoration does look very nice. However, while doing my first water change with this in the tank (about a week after adding it) I picked it up to rinse it and TONS of small particles came off of it! When I looked closer I saw that the outer layer of the decoration was deteriorating, so the particles definitely came from this decoration.

I had to immediately transfer my betta over to a temporary bowl while I cleaned the tank (which took forever!) because the particles look exactly like his food pellets and I'm sure he would have tried to eat them!
1053896
Very disappointed
After a few times used, there is a lot of white things that came on the metal part, and it comes out w the water. Do not recommend
3561840
I would give this 5 stars, but no matter how much I mix it, there are white bits it leaves. I can shake it stir it, and so on, and it has white chunks. Other than that it seems to work great. Just don't dump it in the tank. Mix well 1st.
3239637
Weve had this kettle for almost a year. I absoluetly love it as does everyone else who comes to our house. One issue.... and its been bugging me lately.... heres white spots on the bottom of it. I don't know if they're mineral deposits, mold, etc. Ive always followed manual instructions- hand washing it, never leaving water in it, and so on. But not knowing is making me worried and I don't like using it as much.
1276494
It puts a white dust out onto everything. We had it in the same room as some fish that were in 3 different tanks and they all died 3 weeks after getting the humidifier. The fish's water was getting cloudy the next day after we would change the tanks. It made us wonder what kind of air we were breathing. After the white film would collect on a surface, it was hard to remove. The humidifier had a nice hum to it which helped with sleep but would turn of randomly and disturb your sleep. We liked the idea of not having a filter but this was by far the messiest humidifier we have had.
4495910
It's packed with Sodium Metabisulfite - which is a preservative.  Look that up before you decide to buy.  Tossed it out.