Not looking to start any bio media battles just wanted to ask what the best option would be in addition to my 440 scrubbies & 4 gallons of bio balls? I was thinking a big brick of Cell-Pore or say 15 liter's of Ehfisubstrat Pro in some media bags... I don’t have any experience with either but I'm looking to fill up the extra space in the return side of my W/D. The water won’t be flowing directly through the media but rather over the top it seems (see photo)
Thanks

Thanks
