asking for advice

[arthur simpson]

Aloha!    from Kaimuki on the lovely island of Oahu! Our yard is at about 700 foot elevation directly behind Diamond Head. We have a great view! This is my first post!

I'm just starting to put my system together and have absorbed as much as I'm able on an ongoing basis. My personal goal is to - when it comes to filtration, design a filter that will reduce all solids from the fish to enable the greatest amount of nutrients available for plants. I've studied swirl filters and filters with all sorts of support for bacteria - that all appear difficult to clean, and kind of just sit there.

I've come up with an idea I'd like some feedback on from anybody interested. I have about a 4,400 gallon fish tank divided into four separate tanks. I really don't have enough space for growbeds to justify this but will have less fish and allow them to grow larger to find a balance. The filter is the issue.

So I'm looking at getting a 4 foot diameter by 6 foot high plastic tank (I have one of these for water catchment - 500 gal.) and filling it with golf ball size Wiffle Balls. The plastic balls float. The idea is to pump the fish water in at the top of the tank, 80 gallons per minute,  to cause the thousands of balls to swirl around in the tank, floating, with the solids from the fish water getting beat up as they are mushed by the balls moving around. The Wiffle Balls will have holes all around. The interior of the balls will be untouched and provide a safe harbor for the bacteria. They could have some filter material stuffed into them for additional surfaces but not sure if this will help. I'd pump some additional air into the tank to nurture the bacteria.

In the center of the tank at the bottom, where any remaining solids would gravitate to, would be the exit pipe leading to two, two foot deep growbeds - one with watercress growing in lava cinders (6' X 6') and one with Kalo, or taro, (6' X 16') growing in lava cinders. These tanks would be the final filtration after which the water would move to floatation growbeds. My hope is that the water would be nutrient rich, and there would be no solids buildup creating problems with anerobic zones. I'm trying to create a self cleaning system as well.

May I have your thoughts?!  Thanks, Mahalo, for you help. Art

[Japan Aquaponics - アクアポニックス 日本]

Understood Arthur... I still wonder if you might be over complicating the issue and letting yourself in for filtration difficulties, especially as you are adding the DWC.  Just pump from your FT to the GB - your pump will chop up the fish waste any way.  An easy way to ensure good solid waste distribution would be to have the water flow into the growbeds from a pipe grid like this:

Delivery will go all around the bed that way.  I would also add worms into your system to break down the solid waste.  Solid waste is broken down by heterotrophic bacteria which consume a lot of oxygen - oxygen that would be better served being used by your plants.  They also multiply significantly faster than your beneficial bacteria and so that can be a problem too.  Worms do the job quickly, thus benefiting your plants and good bacteria.

Some people remove the solids, deal with their breakdown separately (worms and lots of aeration), and then return the mineralised nutrient rich water back into the system.  It gives a lot more control in the long run.  Just a thought.

[arthur simpson]

Thanks Japan Aquaponics and George for your thoughtful comments.

I cannot gravity feed from the fish tanks.

I was trying to preserve the solids in the system for their nutritional, mineralization, value - not remove them. In order to immediately enhance their disintegration and prevent ares of anaerobic zones in the growbeds, I was thinking of the Wiffle Ball idea. So the Wiffle Balls are just for the mashing, with the interior of the balls providing primary surfaces for bacterial growth. The cinder beds would be the "sophisticated filtration process". Coarse cinders at the bottom and finer at the top. The first beds the water would travel through are the watercress and Kalo. The roots of both will permeate the beds to three feet deep and provide excellent filtration.

[arthur simpson]

[George]

It really is interesting how much thinking a person tends to when planning a system.  Not having tried this I don't have much of an opinion, other than to say that I don't know of anyone who has found this to be necessary.  A gravel filter (grow bed) works well and you would then have that space to plant in.  I've read about people using entire IBCs for a grow bed which is a really large filter with the same footprint as an IBC cut in half, which most people do.  Good luck.

[Japan Aquaponics - アクアポニックス 日本]

I don't mind having a stab at answering your question arthur.  There are a couple of different types of solid waste in our system... big solid waste, and fine particulate waste (suspended solids).  The big waste is much easier to handle as it can just be swirled slowly and will fall away.  Now when you break that big solid waste up and it becomes increasingly finer and finer... then you need an increasingly sophisticated filtration processes to remove it.

.

So... the swirl filter is passive and gentle because we are trying not to disturb the solid waste too much as it will then not break up and we can remove it more easily.  If you have very fine suspended solids in your system then they are more likely to make it through the growbed and into your raft system... which is not what you are after.  If you can gravity feed the water from the fish tanks to the swirl filter then even better - the pump will not chop the solid waste up at all.

.

Finally, if you have growbeds already in your system, then they should provide all the biological filtration that you need - so the wiffle balls may be unnecessary (unless they were just for the mashing!).    I hope that helps a little.