Ok I am really hoping the answer to this is "Nothing"
I have been searching and researching this for about a year but only got into doing something a few moths ago after I lost my company . I have given the spec's of what I was doing but will rehash ,just so no one has to go looking . I know this is not rocket science but in the back of my head I keep thinking I'm going to F'up something . Tuning I understand ,failure would be a big problem .
Fish tank is 1550 gallon poly water tank that I will cut part of the top off for access . At this point I have dug a hole ,that about took the wind out of me ( not hole digging country ) to set the tank so that 32" of the 48" water level will be below ground level ( 16" of water above grade ) .
The pump is a Mag drive 1800 GPH pump that will be external off a tank bung about 3" off the bottom of the tank .
Air will be from a 200lpm (8cfm) pump to 2 air-membranes and maybe some air in the GB's
I was going to run a 4000GPH pond filter as I do plan to run some DWC and NFT on the system on top of the Fill and drain beds but I am not sure if I am just being redundant and may leave it out of the equation for now .
For starters I plan to build 4 -3'x6'x16" flood and drain beds with Affnan's bell siphons as this is all that will fit in the greenhouse till I can afford to expand it . I will just have to adjust the fish load for the beds and not the tank .
Now some things or should I say details I am not to sure of . First off on the bell siphon . How much drop out of the bed do I need to get a good flow and should the return line be below my bed drops or just below the beds ? As the bell siphons will be using 1" exits what sizing should I use on the main drain line back to the tank , I was thinking 2" should be ok . The one thing I am trying to do is keep the beds from being too high and yes I understand the first rule of plumbing " S##T Runs Downhill " So I do understand all drains have to have a fall rate to work . The only thing I keep thinking is to keep the beds lower I have to either dig the tank deeper (I would hate that ) use a sump ( but that would entail another pump and digging another hole ) or just raising the beds up . Since my water level will be at 16" and the beds will be 16" that is already 32" with no drops in the runs or drops on the siphon . I also would hate to have to get on my knee's to do anything with the fish
So any simple input or am I just getting too anal I just can't afford any costly mistakes at this point .
Have A Kind Day
Mike