Backyard Aquaponics
A place to discuss aquaponics

I know that this is a simple mathematics problem but I cannot figure it out. I feel like a complete idiot for not being able to figure this out and even thinking along these lines in the first place. Maybe I am overcomplicating things? I just don’t want to end up buying a ton of cool aquarium gadgets such as a UV sterilizer just to have something break because I did my math wrong.

I thought of a new design for my living room aquaponics system. If you have not read my other post, I have a 200 gallon aquarium in my living room. I will be keeping fancy goldfish in this aquarium. The purpose of the grow bed which will be located above the aquarium is to filter remove harmful ammonia and nitrates from the water column. I also want to grow plants not only for the benefit of the fish but to clean the air and add some life to my basement apartment. I want this to be as completely self-contained as possible with little or no maintenance. At most all I want to do is add water occasionally because of evaporation. So water will be pumped from the aquarium into the grow bed through a Solid Lifting Overflow. There will be a bell siphon that will dump the water from the grow bed into 75 gallon sump tank. Then I want the water to be pumped continuously from this 75 gallon tank to a uv sterilizer and then to the aquarium. For this design I am assuming I will need two pumps: one to pump the water to the grow bed and the other from the sump through the UV sterilizer to the aquarium. Please correct me if I am wrong in needing two pumps and tell me where in the system would put the one pump.

Now the recommended turnover of water from a fish tank through a grow bed is one time an hour, correct? So if the total volume of my grow bed is 150 gallons (96" x 30" x 12"), I theoretically will only have 38 gallons of water that the grow bed can hold at any one time (150gal x 0.75 usable media = 112.5 gallons of media, 150-113 = 38 gallons of water). So if I don't put a pump on a timer and have the bell siphon dump the water as needed, the pump should fill the grow bed 5 times in an hour, dumping the water into the 75 gal sump every 12 minutes.

Now I have been reading at aquariumproducts.com that to effectively sterilize the water with UV for bacteria and some virus, I will have to turnover the water column 1 to 1.5 times an hour through a 25 watt UV. This is level 1 sterilization. If I want level 2 sterilization (bacteria, stubborn viruses, and parasites), I will have to have a turnover of 2 to 3 times per hour through a 40 watt UV. Quite frankly a 40 watt UV is way out of my price range (approx $600). So I have chosen a UV sterilizer that can do level 1 sterilization effectively at a maximum flow of 750 gallon per hour. The minimum flow is 50 to 75 gallons per hour to prevent the UV sterilizer from overheating.

So how do I design/balance this system out? What gallon per hour pumps should I looking for to pump the water from the aquarium to the grow bed and the water from the sump through the UV sterilizer into the aquarium? I want the aquarium to have a consist water level of 200 gallons. The tank water needs adequate time in the grow bed so that worms, bacteria, and plants can do their magic removing ammonia and nitrates from the water. I don’t want the 75 gallon sump to overflow nor become dry. I want a consistent flow from the sump through the UV sterilizer to the aquarium so the UV can do its magic by preventing algae and killing most harmful bacteria and viruses. I am assuming the UV sterilizer will break if it runs dry for any length of time.

Is this even possible?

Maybe I'm missing something but this sounds like a one pump setup to me. Two if there is a pump on the UV sterilizer

The first thing I would do is get rid of the siphon and run Constant Flood so that the sump water level doesn't fluctuate and it can remain full. I would put the pump in the sump tank where it would pump up to the fish tank. The UV light can be a side loop off the inlet to the fish tank (I'm not absolutely certain how this would be done) or you can just have it take in fish tank water and pump back into the fish tank. The SLO in the fish tank should be a gravity flow (no pump) to the grow bed.

I think you need to draw out a diagram of the components showing the level of each and I think that will help people get a handle on what you're doing. You may want to look into CHIFT PIST or Constant Height in Fish Tank, Pump in Sump Tank - it sounds like what you're doing except you're adding a UV sterilizer.

Or you could just ditch the sump and get an appropriate canister filter (with or without uv light) for the size of your aquarium. If you have already got a uv plumb it on the canister to gb side and put it on a timer (saves power and extends the life of your UV. For the gb run NFT or continuous flow, lighter and more o2 for the plants and fish and the plants grow quicker. To avoid stupid accidents put a small hole on the intake side of the canister about 2" below aquarium normal fill level.
You will still have to do some maintenance but thats the penalty of running a small system.

Or put the UV steriliser on a smaller branch... all of the water doesn't need to go through the UV unit every time around. Run 10% or 20% of the flow into the UV to get the exposure time you need.

Yep... that is what I am going to do. I have been discussing this on other aquaponic discussion boards. But I have yet to receive an answer for this question. I am pretty determined to use red worms in my grow bed. They offer more benefits than just eating fish poo. But I filter the water through a canister filter then UV sterilizer to the grow bed then back into the aquarium with a bell siphon, I am afraid the worms will not get enough food to do their magic. So I was thinking of splitting the water before reaching the canister. Some of the water will be directed to the canister and some of the very dirty water carrying food to the worms will be directed to a water pump which would pump the water directly into the grow bed. The water returning to the aquarium from the canister/UV sterilizer will go through a spray bar so that more oxygen is added to the water column for the fish.

Can this be done? What does splitting the water before getting to the water pump and the canister do to the head pressure? Would I need to add a powerhead inside the tank? The top of the entire aquaponic build will be six feet. The canister I have in mind has a 525 gph rating with a maximum head height of 9 feet. They recommend this canister for aquarium sizes up to 175 gallons. If you have a bigger tank, they suggest buying additional canisters. Should I look for a water pump with the same stats? Maybe something with a higher gallons per hour rate and a higher head height?

Let me know your thoughts.

Thanksfully yours,
Keightley