I am getting a sand filter, you know like for pools, and it is used. It is free in exchange for the three biggest koi in the pond, which is cool because I wanted to get rid of those and get more shubunkins. Have any of you used this type of filtration? I looked around a little and found that the sand was actually not a good idea but instead use bioballs. Both the sand filter and the bead filter look the same on the inside. Any input would be great! Thanks.