Prefilter for Grow Bed

I wrote this post last night but there is something wrong with my blogger apps, so I have to type it again. I made a biofilter during the weekend for my aquaponics system. From my research, I found that for a system this size, the extra filtration is not required as the bed itself is capable of filtering that 80 gallons of fish water. I made it anyway because it is cheap and easy to built plus an extra filter should do some good somehow, isn't it?

I thought building the biofilter is an easy job but it turned out it is not! What was suppose to be an hour job has now turned into half a day job and I'm not even finished yet. There are two problems I'm now currently facing. One is leaking and the other one is the water in the biofilter is syphoned back into the fish tank whenever the water pump is turned off.

I managed to solve the leaking problem, for now. The problem is caused by the 'ribs' at the bottom of the bucket (container)  I used for the filter. The ribs are there to provide extra support to the base. I'm sorry I forgot to snap a picture. I'll update that later. So I sanded it down using my vibration sander and it seems that the problem is gone, for now. If it still leaks I would have to seal it with silicon. I'm trying to avoid using silicon for now as it might be bad for the fish.

Then, the next problem. I know this could happen as the filter is placed higher then the fish tank. So, when the pump is turned off, the water will travel back down into the pump and the pressure it created pull all the water from the filter back into the fish tank. When this filter has actually run, the bottom of it will be filled with solids (fish poo, food remains etc) that is bad for the fish, so I don't want that to enter the fish tank! So now I have to think of something to solve this problem. I need something to relieve the pressure or I could use a valve, and I leave that for my next posting.