hydroponic flow rate

22 years ago

Hi all,

I have a new project under way, in which i wish to grow some amazonian plants hydroponically, using water from an aquarium to provide the nutrients (its a planted aquarium, so i add fertilizers and micro / macro nutrients to this). See the link below for more details.

My question is this...

given my grow tray will be a 5'x 8" trough, with expanded clay pellets as substrate. the water will be pumped from the aquarium at one end, and will drain to a return at the other end of the trough. What kind of flow rate am i likely to need for this setup? I want to keep it as low as possible, as i use CO2 in the aquarium, and this will be gassed of when passing through the hydro tray. Too much flow will mean i loose too much CO2 from the aquarium, and will cause me problems there. but i dont want to starve the plants in this part either.

also, would i need to keep the flow on 24/7? or would it be suitable for some sort of timer? if so.. what hours. Ideally i would have it running at night, when CO2 levels are high in the tank, and therefore i could afford to loose more via the hydro system. Having it off during lights on would reduce CO2 loss, but i have a feeling this would not be really suitable for the plants.

any tips appreciated. Thanks,

Here is a link that might be useful: more info thread

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Comments (4)

willardb3
22 years ago
I don't want to rain on your parade, but I saw a talapia/tomato, fish tank/hydro set-up in Florida and it made lousy tomatos. I really don't know the parameters, but I think a very careful matching of nutrient-fish poop is important. My gut take is that the fish didn't produce enough of the right kind of stuff for the tomatos.

My recirculating hydro uses 0.25 gpm/plant and I run the pump 16 hrs/day, but have run 4 hrs/day with little effect.
kingborris
Original Author
22 years ago
thanks willard3

was the talapia setup planted? mine will be heavily planted and dosed with nutrients. i grow my aquatic plants well enough... i have to trim weekly and remove new plants every month or so to prevent it from becoming over grown. not sure how the nutrient requiremnets of aquatic plants differs from those of terrestrial, but ammonia / nitrites / nitrates should be provided by the fish, and everything else from the nutrients i add. a fish only tank wouldnt provide the right balance of nutrients for any plants, aquatic or not. I was also considering adding a little flourite into the clay pebbles substrate to aid in fertilisation... but that may not work and might cloud the tank... will have to experiment to see.

is that flow rate gallons per min per plant? so roughly 55 litre per hour per plant... that should be do-able. what sized grow tray does that work on?

Thanks,

KB
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baci
22 years ago
Your nutrient concentration & water temperature are important. An extreme example of the effects of salts on tilapia is the Salton sea. Fertilizer runoff from major agricultural areas nearby hypersalinates the sea. Salt water carries less oxygen than fresh water; hot water carries less oxygen than cool water. As the salt concentration & temperatures increase fish suffocate. In 1999, 8 million fish died in a single day Â not mentioning the botulism & dead birds that occurred because of this mess. I am sure your salt concentration will be much less than the seaÂs, but it is food for thought.
willardb3
22 years ago
0.25 gallons per minute per plant flow rate is for 6"dia piping.

There are 4 plants per leg so that flow is 1 gpm/6" leg.

There are 3 legs so total flow in 6" dia piping is 3 gpm.