







🧪 Transform your tank into a thriving underwater oasis — stress-free and stunning!
API STRESS ZYME is a 16-ounce aquarium cleaning solution packed with over 300 million live beneficial bacteria per teaspoon. Designed for both freshwater and saltwater tanks, it naturally consumes sludge and organic waste, reducing maintenance and promoting a healthy biological filter. Trusted for nearly six decades, this weekly treatment keeps your aquarium clean, balanced, and vibrant with minimal effort.













| ASIN | B000255N3W |
| ASIN | B000255N3W |
| Best Sellers Rank | #3,565 in Pet Supplies ( See Top 100 in Pet Supplies ) #21 in Aquarium Water Treatments |
| Brand Name | API |
| Color | multi natural |
| Country of Origin | United States |
| Customer Reviews | 4.8 4.8 out of 5 stars (12,025) |
| Date First Available | June 20, 2004 |
| Date First Available | June 20, 2004 |
| Department | Unisex-Adult |
| Department | Unisex-Adult |
| Directions | Use weekly for a healthy, clean aquarium and to maintain a strong biological filter. Shake well. Using dosing cap on bottle, add 5 ml per 10 gallons (38 L) of water. For new aquariums and to help boost the biological filter, double the dose at start-up and use for 2 additional weeks. |
| Is Discontinued By Manufacturer | Yes |
| Item Dimensions LxWxH | 10 x 10 x 10 inches |
| Item Package Dimensions L x W x H | 8.48 x 2.36 x 2.28 inches |
| Item Weight | 544.31 Grams |
| Item model number | 56E |
| Item model number | 56E |
| Manufacturer | Mars Fishcare |
| Manufacturer | Mars Fishcare |
| Manufacturer recommended age | 1 month and up |
| Material | Plastic |
| Model Name | STRESS ZYME, 16 OZ |
| Number of Items | 1 |
| Product Dimensions | 10 x 10 x 10 inches; 1.2 Pounds |
| Size | 16 oz |
| Style | Freshwater |
| Target Audience Keyword | fish |
G**O
Clear water
It works great. Keep my water crystal clear.
A**6
Amazing product. Really works.
I use this weekly, RELIGIOUSLY. I do not miss a dose. This is my tank today, having not touched the filter in 18 months. (Fluval FX6 filled with only biohome filter media and polishing sponges.) I’ve only changed out the live plants when needed (pothos houseplant clippings) and used the magnetic algae glass scraper when needed. It’s a 75 gallon tank. I8 MONTHS!!! I highly recommend this product. Zero odor, zero nastiness.
J**N
Great for my aquatic frogs
I use this religiously with my African dwarf frogs! They are still kicking strong after 3 years so it must be working!
A**S
Good 👍
Cleans good fish tank.
C**G
... used Stress Zyme for quite awhile and had relatively good experiences with it
I've used Stress Zyme for quite awhile and had relatively good experiences with it. More recently though I've moved to Seachem Stability and found that I prefer it. The Seachem product is more expensive but I've had great success with their line of products and find that Stability works great. Having said that I don't' want to give a negative impression of API's Stress Zyme. It does a good job of establishing and maintaining your biological filtration which is solely responsible for keeping your tanks nitrogen cycle in check. The Stress Zyme, like other "bottled bacteria", is a blend of anaerobic and aerobic bacteria and a "slime coating" agent that helps keep fish happy and healthy. The bacterial agents don't seem to be as "potent" as some others I've used like I mentioned earlier. But, the slime coat portion is more noticeable. When Stress Zyme goes into the water you can see that it has an almost oily consistency that rapidly dissipates into the water column and I'm sure does a good job of keeping your fish... hmm... lubricated (for lack of a better word). Water parameter tests have come up good with API Stress Zyme and there seems to be no negative effects on any of my fish or plants from using or even overdosing it. It's relatively inexpensive and does a good job. If you can't afford Seachem Stability (which I think is a better product) I wouldn't hesitate to recommend Stress Zyme.
D**E
Good value.
It works.
S**R
10/10
Works really well with my tank keeping the water clear and helping reduce sludge on the filters which helps maintenance and keeping it running longer
V**G
Great product and reliably works!
Have used Stress Zyme for many, many years now in my tanks. It really does work. Some know-it-alls, claiming with their PHd's, ect. on fish forums, that this is bogus, that there is no live culture bacteria and can't work, that living bacteria cannot be kept alive in a bottle of liquid. Hogwash. Their medicine they take, such as liquid penicillin... is exactly that. Live bacteria in liquid form. In a bottle. Also that penicillin, the fact that it works, proves THIS bacteria also CAN and does work. The over edumacated people need to get educated on their facts and get them straight. Good bacteria culture NEEDS adding to your tanks to make them more like a good natural made spring fed lake or pond system has, good bacteria that 'mother nature' naturally adds. I have an irridescent shark in my tank, have had him/her since 1997. He/she is still healthy, never had any illness that needed treating. Even when I had other fish in the tank with it, this Stress Zyme cultures kept down the smell that a normal tank normally has. I can open the lid and sniff and virtually smell nothing. If I run out, and not use any for a while, the smell comes back, builds up. Start adding Stress Zyme again and the smell goes away. Fish are more alert and calmer with this added. Irridescents are very skittish and splashy fish. If they are calm, and if there is no smell to your tank when using this, then that means this stuff is working. 2 thumbs up.
S**N
Have used this product religiously on my water changes and don't ever see that changing
S**M
Producto muy recomendable!el agua no se enturbia para nada,hay que tener un buen filtro,el mio no funciona bien y el agua no esta sucia pero huele mal por el filtrado,el producto es buenisimo.
S**A
I love the brand
D**S
I was having some issues controlling nitrites. Used it, two days later, down to zero and stable. I don't see any issues with my Ph, fish, snail, shrimp and plants. I'll keep dosing the water as instructed.
S**E
My regular go to solution after water change.. this has helped my ponds as well as big tanks for maintaining good bacterial colonies in sump and canister filters
Trustpilot
3 weeks ago
2 days ago