Going on 6 years of using matrix in discus tank. I now have a year running it on my 330 gallon reef. Started with 2 liters of matrix. Now I run 2 liters of matrix and 4 liters pond matrix. It made a big difference. I have cut back carbon dosing and love the fact that's it's a easy and natural way of addressing nitrate.
What's the difference you might ask? Size
I had 2 liters of siporax but removed it as I want to try the larger ones. But at this rate I have been with out the siporax over a month and no changes in parameters. I now have an additional 4 liters of pond matrix I am adding tomorrow.
At this point I hope to be off carbon dosing entirely.
I must address the film build up part and will be posting my experience. Same applies to all media. If you noticed on the above pictures I am trying 2 methods with one goal in mind, maintenance.
So after years of using seachem matrix in a canister with great success on my discus tank. I have noticed that yes a film builds up on any media and can be easily dislodged and removed (I must admit I am not entirely sure the film is causesing any degradation in effectiveness of the media)
Down side? bacteria exposure to air if not handled correctly can start to die off and cause mini cycle while it re establishes.
I later started to run 2 canisters and clean out one unit one month and the other a month later. I do this to address redundancy and reduce the probability of a mini cycle as I like to rinse media with discard water by giving it a good shake to dislodge film and possible detritus.
Back to my reef and what is working. I have decided to try high and low flow areas while also creating removable compartments so one can perform maintenance and not impact all the media.
Doing this allows me to grab one of the 1 liter media bag and shake and rinse it in discard tank water at any given schedule.
I also left pond matrix lose in bottom of my filter sock chamber (please note if using pond matrix for the first time please let it soak in water and sink, as they can float due to micro bubbles being trapped in very porous media).
I will try to post a full write up of methods and results as I go along.
Hope this helps.