A Community and Forum For Aquaponic Gardeners

Lighting and Grow Bed Size

Hello all!

I am very new to the hobby and was curious as to what size grow bed I can maintain on an interchangable HPS/MH 600 watt setup with a 120 gallon fish tank?

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Permalink Reply by TCLynx on December 17, 2012 at 11:42am

I personally like to base my media bed volume on the fish tank volume (like tend to recommend the media bed volume at least equal the fish tank volume if stocking will be kept minimal and if one is likely to stock to the max fish tank capacity, one then needs to have twice as much media bed as fish tank volume, which of course means you need some way to deal with water level fluctuations.)

As to how much square footage that light can cover, I'll have to let the lighting gurus answer. If you add a light mover, you may be able to have a bit more grow bed space without additional light fixtures but I'm in Sunny FL so I don't have much hands on experience with such things since I tend to just grow right outdoors.

Permalink Reply by Jon Parr on December 17, 2012 at 11:53am

600 W is generally good for a 6' x 6' area, which gives you 36 cubic ft of growbed at 1' deep, enough for a max of 36 lbs of fish load, which is about the max for your tank as well. 25-30 lbs would be safer

Have fun

Permalink Reply by Hector Chavez on December 17, 2012 at 1:37pm

Is the 6' x 6' ok for a stationary light or were you thinking of a moving light?

Permalink Reply by Jon Parr on December 17, 2012 at 6:51pm

You might be able to stretch that figure, Hector, especially if you have some natural light. Light movers typically get you better growth in the area that you have (by eliminating shadows and dispersing intensity), but not necessarily more area. Give it a shot, let us know.

I'm personally a fan of vertical bulbs with no reflector, and the plants positioned in a cylinder around the light. That way there is no loss from reflector or glass, and no hot spots from a reflector. Vertical bulbs cool naturally by convection, and can be yo-yo'ed up and down vertically to eliminate shadows.

Permalink Reply by Hector Chavez on December 18, 2012 at 11:46am

Excellent I like the vertical light Idea, very clever. I think I am going to start out with a smaller grow bed 12-14 square feet just until I get the knack of things then I think I will try the vertical set up.

Permalink Reply by TCLynx on December 18, 2012 at 9:09pm

Keep in mind that vertical can get tricky if you are dealing with a low ceiling basement and tanks sitting on rather than sunk in the floor. You only get so much vertical growing space and most vertical planting methods are really only good for the small plants that don't get terribly tall on their own. Now I suppose you could have tall plants set up in a circle around the light and yo yo it between the plants but then you are only getting light on one side of the plants (which may or may not be an issue, I've personally never tried it.)

Back to vertical growing, remember that vertical growing you have to pump water up higher which usually takes more power and generally you are dealing with small flows to each vertical which tends to have far more issues with clogging so keep this in mind when designing, verticals should generally be getting checked daily to make sure water is flowing properly. In a hobby system going away for a long weekend without checking the towers is only a minor risk if the feed design has had most of the clogging issues worked out of it but if you are having to unclog many towers on a daily basis, then you can expect that many towers will be drying out or dead if you go on holiday without some one taking care of it for you.

Permalink Reply by Jon Parr on December 18, 2012 at 9:41pm

Amen to the clogging issue, TC, and I don't have a solution to that yet. It's a big enough problem that I don't have any vertical systems growing right now that need to be individually metered like Zip-Grows or the like.

However, when growing around vertical bulbs, with or without a yo-yo, the plants grow both up, and towards the light, resulting in stems that go up at a 45 deg angle (more or less), and the effective lighting is from the "top" (relative to the plant). Vertical growing can be done in vertical tubes like Zip-Grows, or stacked horizontal pipes, or shelves that terrace down, one to the next. The shelf idea allows one singe pump output, and thus eliminates the need for multiple small lines that are a maintenance issue. I have some tomatoes potted in compost that sit in shelves lined with DuraSkrim right now, pretty easy to maintain. They just wick up what they need, and watercress (no media, just dropped on the film of water) fills the space in between the pots.