I made one of these filters

http://www.skippysstuff.com/index.html

for my 100 and 130 gallon ponds. I scaled it down as these are for large ponds. I used a 5 gallon bucket for the filter, then attached a got a large pond pump. It works well and is pretty easy to make.
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0.1.0 ornate box turtle
2.0.0 eastern box turtles
1.0.0 Yellow belly slider
0.1.0 Red belly cooter
0.1.0 Australian shepard
1.8.0 chickens
1.0.0 Dutch rabbit
3.2.0 adult children
1.0.0 husband
AND
0.1.0 grandbaby!!