Just finished up this DIY filter for the 130g koi pond I just put in last week. Quick run down of what parts I used are as follows...
2.5g bucket with tight fitting lid
730gph submersible pump
Hose
Matrix pond media
Filter floss
Light diffuser section
Basically it works as a bottom draw canister filter where the pump draws in water through all the holes drilled into the bottom of the bucket. It then flows upwards through the matrix pond media and then the second stage is the filter floos for water clarity.



