CRYSTAL Aquarium Filtration Media Cartridges for Superclean 40 Internal Filter, Size 1, Pack of 6

I bought a rena fish tank which looks great but didn't realize how expensive the bits and pieces for the filter was but I can say that these are a good price. They do work fab once bought.

found them very effective, even tend to have them for 1 or 2 weeks longer than recommended. We have 2 healthy living goldfish for 4 years now, and I put it all down to this filter great work.

Didn't do anything for my tank

Getting 6 of these instead gd the usual 2 (as sold on Pets at Home, for example) works out more cost effective.

worked

Good performance and easy to install in our filter.. the box claims the filter lasts three weeks but I'd not leave it longer than 2.... Still a solid recommendation.

Always get these filters. They work a treat

This was the best price I found for these Crystal Cartridges and they are great at keeping the tank water clean throughout the month.Change them once a month and fish stay healthy and well.