---
product_id: 49040210
title: "Cycle Biological Enhancer, 250 ml ( Packaging may vary)"
brand: "fluval"
price: "$29.49"
currency: USD
in_stock: true
reviews_count: 13
category: "Fluval"
url: https://www.desertcart.us/products/49040210-cycle-biological-enhancer-250-ml-packaging-may-vary
store_origin: US
region: United States of America
---

# Safe for plants, fish & humans Eliminates toxic ammonia & nitrites Instant beneficial bacteria boost Cycle Biological Enhancer, 250 ml ( Packaging may vary)

**Brand:** fluval
**Price:** $29.49
**Availability:** ✅ In Stock

## Summary

> 🦠 Transform your tank into a thriving aquatic paradise—because your fish deserve the best!

## Quick Answers

- **What is this?** Cycle Biological Enhancer, 250 ml ( Packaging may vary) by fluval
- **How much does it cost?** $29.49 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.us](https://www.desertcart.us/products/49040210-cycle-biological-enhancer-250-ml-packaging-may-vary)

## Best For

- fluval enthusiasts

## Why This Product

- Trusted fluval brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Toxicity Eliminator:** Effectively neutralizes harmful ammonia and nitrites, ensuring crystal-clear, safe water.
- • **Eco-Friendly Formula:** 100% safe for your fish, plants, and even you—no compromises on health or environment.
- • **Rapid Aquarium Startup:** Jumpstart your tank’s nitrogen cycle with powerful bacteria for a healthy aquatic ecosystem.
- • **Trusted by Enthusiasts:** Top-rated with thousands of happy fishkeepers relying on Fluval Cycle for thriving aquariums.
- • **Consistent Water Quality:** Use regularly to maintain a balanced biological habitat and prevent water quality spikes.

## Overview

Fluval Cycle Biological Enhancer is a 250 ml liquid supplement designed to rapidly establish and maintain a safe, biologically balanced aquarium environment. It introduces beneficial bacteria that eliminate toxic ammonia and nitrites, promoting healthy fish and plant life without any harm to your aquatic ecosystem. Ideal for new tank startups and ongoing maintenance, this product is a trusted choice among aquarium enthusiasts for ensuring crystal-clear, safe water conditions.

## Description

Product Description Fluval Cycle biological aquarium supplement for new tank startups and regular maintenance 250ml. Directions The product_description from the external source provides the following instructions: 1. Use Fluval Cycle Biological Enhancer for new aquariums to establish safe and essential conditions. 2. Apply the product regularly to competitively exclude undesirable bacteria in aquariums. 3. Add the product to aquarium water to eliminate toxic ammonia and nitrites, creating a biologically well-balanced aquarium for healthy fish to thrive. P.when('A').execute(function(A) { A.on('a:expander:toggle_description:toggle:collapse', function(data) { window.scroll(0, data.expander.$expander[0].offsetTop-100); }); }); Box Contains Cycle See more

Review: Maintain a healthy Aquarium - I use this product when setting up a new aquarium (as part of the nitrogen cycle to promote healthy ammonia eating bacteria growth, a 6 to 8 week process) and as part of my weekly water changes. I feel that this product works very well, as my fish are all happy and healthy and I have never experienced any bad water quality issues (ammonia spikes etc). I use this weekly to add to my 200ltr, 60ltr and 30ltr aquariums when I do a water change. I change 20% - 30% of the water volume and add an appropriate dose of this stuff, however it's not really possible to overdose so it does not really matter if you add a little bit extra. I usually do add a bit more than stated on the label. I keep it stored at room temperature and the 2ltr bottle usually lasts me about 6 weeks. There is always a seal covering the opening after the lid has been unscrewed, so you know it is brand new and has not been opened / tampered with. This is safe for my fresh water aquarium inhabitants, of which I have many varieties. Pros: - The larger 2ltr bottle is excellent value compared to the 250ml or 500ml bottles - Quick delivery / repeat orders available - Far cheaper than my local pet store Cons: - Nothing I can think of really I hope this review has been helpful to you. Happy Fish Keeping!
Review: Good - Seemed to work well tank cycled quicker

## Features

- Powerful team of beneficial bacteria immediately inoculates aquarium water
- Creates a safe biological habitat for your fish
- Eliminates ammonia and nitrite
- Will not harm plants; animals or humans
- Size: 8.4 oz.

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B00FPIZ8Y0 |
| Batteries Included | No |
| Batteries required | No |
| Best Sellers Rank | 1,430 in Pet Supplies ( See Top 100 in Pet Supplies ) 13 in Aquarium Water Treatments |
| Customer Reviews | 4.6 4.6 out of 5 stars (6,493) |
| Date First Available | 6 Jan. 2014 |
| Item Form | Liquid |
| Item Weight | 239 g |
| Item model number | A8349 |
| Number of Items | 1 |
| Pet Type | Fish |
| Product Dimensions | 5.84 x 5.84 x 15.24 cm; 239.55 g |
| Quantity | 1 |
| Size | 250 ml |
| Volume | 250 Millilitres |

## Product Details

- **Brand:** Fluval
- **Item form:** Liquid
- **Item weight:** 8.45 Ounces
- **Liquid volume:** 8.4 Fluid Ounces
- **Manufacturer:** Rolf C Hagen UK Ltd

## Images

![Cycle Biological Enhancer, 250 ml ( Packaging may vary) - Image 1](https://m.media-amazon.com/images/I/71CbLgtkAbL.jpg)

## Questions & Answers

**Q: i have a 240l tank how much cycle do i use in my tank it is a new tank.**
A: Tip the whole bottle in your filter

**Q: Can this be used to boost some established bio media in a new tank?**
A: Yes definately. Put it in the tank as instructions say. Then keep putting a min og 10 ml in until your happy. I used it for setting up new 200 ltr tank and it's the only stuff I used after that.

**Q: Can I use this in salt water?**
A: Having read the information on the back of the bottle it says that it is safe for use in fresh and salt water aquariums.

**Q: I want to add new fish into my established tank. Can I add this into the tank, let the bag with new fish float for a while then release the fish?**
A: No! What you must do is add this after following the instructions and leave for a few days for the bacteria to establish a proper environment for the fish before they are added. Try reading a book or 3 on setting up a fish tank.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Maintain a healthy Aquarium
*by M***D on 3 April 2021*

I use this product when setting up a new aquarium (as part of the nitrogen cycle to promote healthy ammonia eating bacteria growth, a 6 to 8 week process) and as part of my weekly water changes. I feel that this product works very well, as my fish are all happy and healthy and I have never experienced any bad water quality issues (ammonia spikes etc). I use this weekly to add to my 200ltr, 60ltr and 30ltr aquariums when I do a water change. I change 20% - 30% of the water volume and add an appropriate dose of this stuff, however it's not really possible to overdose so it does not really matter if you add a little bit extra. I usually do add a bit more than stated on the label. I keep it stored at room temperature and the 2ltr bottle usually lasts me about 6 weeks. There is always a seal covering the opening after the lid has been unscrewed, so you know it is brand new and has not been opened / tampered with. This is safe for my fresh water aquarium inhabitants, of which I have many varieties. Pros: - The larger 2ltr bottle is excellent value compared to the 250ml or 500ml bottles - Quick delivery / repeat orders available - Far cheaper than my local pet store Cons: - Nothing I can think of really I hope this review has been helpful to you. Happy Fish Keeping!

### ⭐⭐⭐⭐⭐ Good
*by A***N on 20 June 2025*

Seemed to work well tank cycled quicker

### ⭐⭐⭐⭐⭐ Used for years.great product.
*by J***N on 19 November 2025*

Does what it says.

## Frequently Bought Together

- Fluval Cycle Biological Enhancer, Aquarium Water Treatment, 8.4 Oz., A8349
- Fluval Waste Control Biological Cleaner, Aquarium Water Treatment, 8.4 Oz., A8355
- Fluval Clarify Bio for Aquarium Water Treatment, 4-Ounce

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*Product available on Desertcart United States of America*
*Store origin: US*
*Last updated: 2026-02-21*