Recomendations on Piping, Ratio and Pump for my IBC Setup

[Raymond D. Lewis]

I local company gave me 4 IBC tanks that were use to hold an FDA approve food grade liquid.  I have cleaned and cutted one of the tanks into 2 pieces.  The first piece is 26 inches deep and will be use for DWC bed. The second piece is around 13 inches deep and will be used as a Flood & Drain Gravel bed. I'm planning to cut another one the same way.  I want to have 2 small DWC beds, 2 gravel beds and one almost full 275 US gallons IBC, probably only using 250 US gallons, for the fish tank with just a square cut on the top for easier access to the fishes. The fourth tank will be use for another project or as spare tank in case on of the others gets broken. Does the ratio of four grow beds to one 275 Gallons Fish Tanks is good?

I'm still a little bit concern about using PVC on the pipes and fittings. I would like to try using HDPE for everything. It is possible to build the siphon, use piping and fittings made from HDPE for IBC based setups or the availability of the parts make this impossible? Roughly estimating, how much expensive is HDPE VS PVC, twice, triple?

The fish tank will hold 275 gallons if the water level is touching the 1000 liter mark. Its dimensions are 3'3"H by 3'3"W by 3'9"L or 3.25'H by 3.25'W by 3.75'L.  The volume of the IBC is 39.61 cu. ft. or 296.3 US gallons or 1121.62 liters. Because I will cut the top to enable easier access to the fish, the tank will probaly hold at the most 250 US gallon or 946.35 liters of water, fish and fish poo.The gravel beds dimensions are 1'1"H by 3'3"W by 3'9"L or 1.08'H by 3.25'W by 3.75'L. Based on these dimensions the volume for each gravel bed is around 13.16 cu. ft. or 100 US gallons or 378.54 liters of water, hydroton, worms, fish poo and plant roots. The DWC beds are most likely to have twice the volume of the gravel beds, 26.32 cu. ft. or 200 US Gallons or 757.08 liters, because the dimensions are the same except for the height which is 2'2" or 2.17', double the height of the gravel beds. The total volume for the entire system is 850 US gallons or 3217.60 liters. For this setup what pump capacity should I use?

For now I would like to focus the discussion on the piping, pump and ratio. I'm not trying to start a HDPE VS PVC thread.  It just a personal decision and I will only change my mind if the going HDPE is not viable in terms of cost and availability only. Also I understand that this mixed system will require some extras like a swirl filter before the DWC even if the water passes through the gravel bed first. I would probably feedback the discharge of the swirld filter back to the gravel beds but I will start another thread for those extras in their corresponding section of this forum.

Thanks a lot in advance.  I consider the people on this forum experts.

[Raymond D. Lewis]

I found on Ebay a seller that suposely sells 1" and 2" polyethylene black bulkheads. The url for the 1 inch is: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=280930169174.  The pictures on the auction are the followings:

1 Inch Bulkhead2 Inches Bulkhead

 

The auction title says Polyethylene but the description only mention the word poly.  Could this material be polystyrene instead of polyethylene?