Backyard Aquaponics
A place to discuss aquaponics

Hi,
Our 150G system has done quite well since the Nitrogen cycle was established. Our goal is to raise Tilapia...not just goldfish.

I would appreciate any input on how to make this better...without too much more expense.

So, I bought a 265G IBC container, cut off the top, and cleaned thoroughly yesterday. Here are my plans based upon what I learned. I had really expensive plans but 'reason' got hold of me.

* Move the fish tank in the garage to the front of a window with a direct southern view.
* Add a grow bed 12" deep and large enough to cover most of the top...in order to get as much media to grow bacteria as possible.
* Install a reflective box around the grow bed to reflect as much light as possible back toward the plants.
* Install 4 sets of 48" plant lights, each with adjustable heights to move as close to the plants as possible.
* Install a bell syphon in lieu of a loop syphon (the bottom 2" doesn't drain with our loop system).
* Add ammonia to the system in order to activate the nitrogen cycle. Allow 6-8 weeks. I believe a test is to add some ammonia one day...and to test the next...it should be 0 ppm...indicating the system is ready. Some suggest urine is good to use...not sure how much.

At that point we would add some Tilapia fingerlings.

Please let me know if there is anything else I can do to enhance water quality, maximize light, etc.

Regards,
Chuck

Hi Chuck:

Sounds like a plan. As we go into Summer you might not get sun into the window except in the morning and evening. In Sketchup you can experiment with the sun at different dates and times of day to get an idea of how light falls on your buildings. This is helpful when you want to maximize the solar gain.

Plan to have enough of a gap above the tank so that you can still reach the fish.

I used gorilla shelving from Sam's Club to put gravel beds over a tank in the basement back in the day, see my 2007 thread. I cycled that with ammonia - if you are planning on using pure ammonia like from the grocery store make sure to shake the bottle. If it foams it has detergents in it that will kill your fish. It also shouldn't have any added fragrance. It is hard to source due to meth labs using it, I went to like half a dozen grocery stores before I found some. Pee is easier and cheaper and probably works just a well.

Also note that the fish don't care about being in the dark, so you might just set the FT off to the side and fill the sunny window-side area with just plants since they are the ones that want the light.

Hi Chuck,

Leaving 2 inches of water in the growbed each cycle doesn't really create any issues. For me, bell siphons were more reliable than loop siphons so I think this is a good change.

Make certain you check for Nitrites before you get your fish, just in case the bacteria for the second part of the conversion process haven't kicked in.

With just the one 12" deep growbed you'll need to go easy on how many fish you stock or you'll have to use supplementary filtration.

Considering all the lighting and the reflective material you will probably need a fan of some kind to circulate air around the plants. You also may see some burning of plants depending on how evenly the sunlight is distributed.

Loop siphons are fine for small growbeds... under 200L... anything else and a bell siphon is preferable...

Hi,
Thanks for the feedback.

That's a good idea about setting the growbed in a different space than on top of the tank...to access the fish and to maximize usage of the window. I'm working up a new sketch now.

Regarding fish poundage, growbed sizes....I played with many calcs last night. Discovered, as mentioned above, there is a limiting factor for the number of fish in a tank...duh! For example, I could go 230 gallons to support 32 pounds of fish (~1 lb per 7 gal). However, the growbed would need to be 32 cubic feet (~1 lb per cubic ft GB)....unless I add additional filtration.

So, limiting the GB to 20 cubic feet (5'x4') I could have 20 pounds of fish. This self-imposed limitation is based upon maximizing sunlight coming through the window.

Another thing is this. A GB of lava rock and pea gravel, if allowed to fill to 12", holds about 40% of it's volume in water. So, a 230 gallon tank feeding 32 cubic feet GB would drain the fish tank about 96 gallons (230 to 134) when filling the GB. So each cycle, the fish would crowd together much more closely.

Does this mean I need to use (fish tank capacity) - (grow bed water capacity) = water which is used to calculate max fish loading?

What sort of supplemental filtering could I add to 20 cubic feet of GB to support 32 pounds of fish? Are we talking a couple of 55 gal drums full of 'something' that grows bacteria? I do recall reading somewhere that there are things with greater surface area that could reduce the size of the filtration media.

I appreciate your thoughts on the matter. Can't begin to calculate how much I have saved by not 'jumping off into the deep end' by building the first system that came to mind.

Regards,
Chuck

Hi Chuck,

I have seen TCLynx advise starting at 1 cubic foot of media (7.5 gallons) per fish that you intend to grow out to 1 lb. Since your system is new this is what I would use for the estimate (looks like your on the right track based on your limits).

You could add another 12 cubic feet of media in a garbage can or two to get your capacity (no need for plants or sunlight).

You could also use a swirl filter (or other filter type) to remove some of the solids which would reduce the load and the amount of growbed space needed.

I suspect that you will find your tank will be sufficient. Your 12" deep growbed will probably only be filled to 10" with media and then the water only comes within 1" of the top of the media. Assuming short pipes, you would really only be looking at roughly 75 gallons including what's in the pipes at maximum flood. You could also design your system growbeds to always have an inch or two of water in the bottom even when draining is complete, further reducing the water needed to flood the growbed between .8 and 2 cubic feet or around 5.9 to 18.5 gallons. This also helps the plants should the pump fail when you aren't around.

You could also try running constant flood with very little water level fluctuation in the tank.

Hope this helps!

Hi Scotty,
I had not thought about that. So the goal is to collect some of the solids and filter it out before going into the growbed and back into the fish tank? I'll read up on the 'swirl' filter...sounds interesting.

Regarding the garbage can...what sort of media would you use? This is an excellent idea...allowing me to maximize fish production...and growing some veggies at the same time...without having a 1 ton + growbed.

Thanks,
Chuck

Been out moving between houses so I missed your post yesterday.

Yes take some solids out before the growbed but hopefully most would not go back to the fish tank (you want it to stay in the growbed or the swirl filter).

I'd probably just use whatever I would use in a growbed figuring that my system would expand in the future. Scrubbies should work and would be lighter than regular grow bed media (but probably couldn't use it for your next growbed just as a filter media). Lots of people making pond filters use the scrubbies. This link shows what I mean by scrubbie - http://www.gardenpondforum.com/scrubbies-filter-t6563.html