# Replacement Biological Filter Media Insert for Fluval U Series (Hagen) — Compatible with U2, U3, U4 (MPN 51870)

**URL:** https://aio.lv/en/product--hagen-51870--12035413
**Data updated:** 2026-04-07 20:34 (EEST)
**Category:** Water Filters
**Manufacturer:** Hagen
**Manufacturer code:** 51870
**EAN:** 015561104951
**Warranty:** 2 Years
**Availability:** Available for order
**Price:** 8.49 €
**Prices and availability valid until:** 2026-07-29 23:59
**Price without VAT (21%):** 7.02 EUR
**Can be purchased by legal entities:** Yes (invoice)
**Buy:** https://aio.lv/en/product--hagen-51870--12035413

## Delivery options

| Delivery method | Delivery time | Cost |
|---|---|---|
| Office pickup (2b. Kengaraga str., Riga, Latvia, LV-1063) | 16.07.2026 | free |
| Pickup points | 21.07.2026 | 1.89 EUR |
| Courier delivery to door | 21.07.2026 | 4.99 EUR |

## Summary description

Hagen replacement biological filter media insert designed for Fluval U internal canister filters, compatible with U2, U3 and U4 models (MPN 51870). Provides biological filtration surface for beneficial bacteria growth to support nitrogen cycle and water quality. Suited for freshwater and saltwater aquariums; used as a direct media replacement to restore biological filtration capacity.

## Long description

Replacement Biological Filter Media Insert for Fluval U Series by Hagen is a spare media element engineered to restore the biological filtration capacity of Fluval U internal canister filters. Designed to fit Fluval U2, U3 and U4 models, this media insert provides a porous surface area that supports colonisation by beneficial nitrifying bacteria, contributing to the breakdown of ammonia and nitrite and helping to maintain stable water chemistry in both freshwater and saltwater aquariums.
Advantages
This replacement media insert offers a consistent porous structure that maximises surface area for bacterial colonisation while maintaining good water flow through the filter. As a direct-fit component for Fluval U2, U3 and U4 units, it simplifies maintenance by providing an interchangeable biological stage without modification. The material is durable for long-term use and can be rinsed to remove detritus without destroying established bacterial colonies when maintained correctly.
Suitable for
Freshwater aquariums requiring biological filtration restoration
Saltwater and marine tanks seeking stable nitrifying bacterial colonies
Owners replacing worn or clogged biological media in Fluval U2, U3 and U4 filters
Routine filter maintenance to preserve water quality and the aquarium nitrogen cycle
Key specifications
Compatible filter models: Fluval U2, U3, U4 internal canister filters
Function: biological filter media insert providing porous surface for beneficial bacteria
Material characteristics: high-surface-area porous media designed for water flow and bacterial colonisation
Suitable environments: freshwater and saltwater aquariums
Use type: direct replacement media for the biological stage of the filter
How to use
Turn off and unplug the Fluval U filter and follow the manufacturer’s instructions to access the internal media stack. Remove the old biological media insert and, if possible, transfer a small amount of existing mature media or filter material to the new insert to preserve established bacteria. Rinse the new insert briefly in aquarium water to remove any dust from packaging, then place it into the designated biological media slot and reassemble the filter. Restart the unit and monitor water parameters over the following days to ensure stable ammonia and nitrite levels as the biological colonies establish.
Usage recommendations
For best results, replace the biological media insert as part of a scheduled maintenance routine rather than all filter media at once. When cleaning, use aquarium water rather than tap water to preserve nitrifying bacteria. After installing a new insert, test ammonia, nitrite and nitrate over subsequent weeks to confirm biological filtration is functioning as expected.

## FAQ

### How much does the Hagen Fluval U Replacement Biological Media 51870 cost, and is it available for purchase?

The price is 8.49 € (valid at the time of publication and already includes all taxes). The item is available for order — 11 pcs. are in stock, and you can place your purchase right now with delivery across Latvia and Europe or choose pickup at the Riga collection point. We offer favorable purchase terms, including the option to split the payment into convenient monthly installments. Availability and price are updated in real time, so we recommend placing your order in advance.

### If I order this product today, when will I receive my order?

If you place your order today, delivery will be as fast and convenient as possible. You will be able to pick up your order on 16.07.2026 at the Riga pickup point or choose delivery across Latvia and Europe. We carefully inspect every purchase and pack it securely for safe transportation.

### What payment options are available?

AiO.lv offers several payment methods: Bank transfer, Bank cards on-line, Apple Pay, Google Pay. All transactions are 100% secure and encrypted.

### Can this product be purchased for a company (with VAT)?

Yes. AiO.lv works with legal entities in Latvia and across Europe. The product price already includes VAT. For certain product categories, as well as for companies from other EU countries with a valid VAT number, a 0% VAT rate may apply. We issue the invoice immediately after the order is placed, support electronic BIS invoices, and automatically generate all necessary accounting documents. You can complete the purchase for a company online — simply select the company profile and choose bank transfer as the payment method during checkout.

### What is the warranty period?

All Hagen products come with an official 2 Years warranty. It covers all manufacturing defects and malfunctions that may occur during use. The warranty is valid at all authorized Hagen service centers and through AiO.lv

### Can the product be returned after purchase?

Yes, you can return the product within 14 days of purchase if you bought it as a consumer (not a legal entity). Returns are possible without giving any reason — the main condition is that the product retains its original appearance and full set of accessories. We will make the process as simple and convenient as possible: just contact our customer support team, and we will help you arrange the return.

### Where should I contact for warranty service?

For warranty-related questions you can contact the AiO.lv (SIA VSPRO) customer support team. More information about warranty service: https://aio.lv/en/warranty

## Image

https://aio.lv/img/cache/product/12035413/67522740_large.webp