Recirculating Systems. Why do we pump water 24/7

[Alan]

Hi, I've been thinking a lot recently about our general assumption that we need to circulate our systems 24/7. After all plants do not take up nutrients in the dark. So they do not need moving water at night. Which leaves us with the fish. They also slow down at night and release less waste (I do not know this for fact for all fish. Apparently they sleep. https://en.wikipedia.org/wiki/Sleep_in_fish included Tilipia.

Recirculating systems why do we pump the system 24/7 ?

Do fish product as much waste at night as day?. (We only feed them in daylight. )

Could we without harm to the system pump during daylight and only aerate the fish tank at night. ?

FYI I'm in tropical Thailand using Tilipia.

Comments advice from Forum much appreciated.

[Jeff S]

Good thought as long as you don't need the extra circulation time to allow your bacteria more time to break down the ammonia and don't have a waste build up. Some systems have timers on the pump to regulate flood and drain. I think Tilapia do sleep based on what I've seen.

[George]

In my flood and drain system, each bed floods twice per day.  Aeration in the tank runs 24/7.

[Jeff S]

I've recently increased aeration and water flow in my tank and the fish are definitely more active and eating more. Been at it for 2 years so I'm a slow learner.

[David]

I used to shut of my pumps at night to minimize temperature drop during winter months. I did not have any issues. 24/7 is not required.

[Jeff S]

I did that at one time before I added aeration. Only had 5 Tilapia and a few goldfish at the time. Worked OK for a few days until the O2 had time to dissipate. Came home one day and the water was covered in slime and the fish were bobbing for air. Talk about panicking. Added air and the problem went away immediately. Like I said, I'm a slow learner. This  forum will hopefully save you some grief.

[Alan]

Great replies. Definitely considering reducing water flow at night. Maybe DO monitoring over a period with different circulation periods at night will be a good experiment. I need to get a DO meter anyway.

Thanks for input. Food for thought (no pun intended....)

[Jeff S]

Save your money. Just pump in a lot of air. Let the return water splash. Build a venturi into you return line. If you're not focusing on aquaculture exact DO #s aren't important. More important would be a backup power supply for when you pumps all stop.

[Alan]

Jeff,

I agree.  I followup on a utube video and did some experiments with some air pumps and non return valves. Put it on my Blog. Link below.

http://siam-aquaponics.blogspot.com/2015/07/air-lift-pump-aka-als-l...  

[George]

Airlifts are a great way to aerate while lifting water and solids.  Regarding the link, I believe it is recommended that metal not be used in an aquaponics system.  

My system has six media beds, which flood and drain twice each per 24 hours, using timer and indexing valve.  In addition, an airlift pumps continuously to 1 bed and that bed also drains continuously - floods completely as do the others, twice per day.

I may change my airlift to pump to a swirl filter, which will drain back to the fish tank.  My tank is in the ground.

Diagrams and explanations of airlift pumps tend to confuse me or at best I have trouble understanding them.  My lift is much like Alan's except without a check valve.  It is a 1 1/4 inch pipe with an elbow running to the bottom of my tank (elbow rests on tank floor, near the center).  An air line runs down inside the 1 1/4 and  releases air near the bottom of the pipe.  At the height where I want the water is a T, with a pipe running off to a grow bed - a riser continues up another two feet or so from the T.  It can be improved upon but it works very well for aerating and keeping the bottom of the tank clean, while using only 40 watts.  The lift is only about 2 1/2 to 3 feet from surface of the water and that's about the limit without modification.  Tank is 4 feet deep.  Depth of tank will affect your results, as will air pump and size of piping, check valves, any variable.  I also use an air lift to filter an aquarium, 1/2 inch pipe, lift about six inches or so.  You can run one of these with a small air pump.

https://youtu.be/G3DBAb4jdBc

[David Marland]

For twelve months now I have used a timer, I set it for hourly cycles during the heat of the day with 15 minute off settings, at night I have the pump off for two hours at a time with 15 minute on settings. But I also use a 24/7 battery backup air pump. With ten hour backup battery life. The electric timers only cost $9 for the two, the air pump cost $135 I hope this will help,

[Jeff S]

Yesterday while I was using my air pump for an air lift pump experiment, the water pump in the my IBC tank stopped. Within 2 hours the fish were gasping for air. It doesn't take long for issues to get critical. I do have a heavily stocked fish tank. I have found that the fish eat a lot more with more air in the water.

[David Marland]

Actually. The other week I noticed my air pump stoped when the timer stoped, the battery must have worn down during the night off periods? So I changed the power cords around so that the air pump is powered 24/7. Now.