Backyard Aquaponics
A place to discuss aquaponics

You could do that with a cable tie actually.... that's not a bad idea.

Technically just cutting up straws into say 1cm pieces would work well as a moving aerated filter imo.

They may be too buoyant though.

I had an idea before to use those plastic golf balls with the holes in them as biomedia, haven't tried it yet though. Not as good as bioballs, but with aeration I think they would move around a like them and hold a lot of bacteria on the outside and inside.

How many square feet of growing is required to support a certain amount of fish or vice versa, how much fish do you need to support a given amount of plants.

Tricky questions since the growing method has a great effect on the answers. Like if you are removing solids, you are removing nutrients but leaving the solids in creates more biological oxygen demand, in some systems this is rarely an issue with flood and drain media but in a constant flood or DWC system it is different.

I've got a fairly new big system going. about 418 square feet of raft bed plus 100 Zipgrow towers as well as one media bed and some seed starting trays, tanks and beds on that one system.
So how much fish being fed 1% of body weight does that need to have good plant growth?
This is a system with little to no solids removal. For simplicity sake I"m going to count each Zipgrow tower as 3 square feet of growing space. They should probably count as 5 square feet though.
So, that would be a total of 718 square feet of growing space (not counting the one media bed and seedling beds on the system.) So how much fish do you think I have had going in that system to grow these plants?



I can guarantee that I'm not running 1 lb of fish per square foot of plant space.
I doubt that system has ever had as much as 1 lb of fish per 4 square feet of plant space. It started out with only 47 large catfish (average probably 3 lb) then I added the large bluegill (40 average 1/3rd lb) so that would have been a total of 155 lb. We have been harvesting the larger fish and I have just added a couple cage of small fish to that system since the water has cooled off and I'm going to be struggling to keep the nutrient levels up here through the cool season.

My media bed system only has aprox 250 square feet of growing space but I have about 100 lb of fish in that system. The nitrate levels in that system are about 4 times as high as the nitrate levels in the other big system.

But can it really be compared? I don't bother growing tomatoes in the big tower/raft system I'll grow those in the media beds where supporting a huge plant won't get in the way of my harvesting and planting large amounts of lettuce for customers. Come Hot weather I expect that several tomato plants and some lufa vines will suck down plenty of nutrients from the media bed system so I'm not going to worry too much about the nutrient levels being a bit high through the cool season in that system. These are living systems and though there are plenty of rules of thumb and even quite a lot of engineering to get something started in the right direction, how exactly it will all boil down in actual practice is going to be answered differently for almost every system out there. Different climates, plants grown and source water are just the first few variables of hundreds and even people growing the exact same stuff in similar climates using the exact same system design are probably still going to have several things different which will make their results vary.

how often should i clean out growbeds? I have 13 bathtubs full of quartz basalt aggregate and havnt cleaned them in 4.5 years. Plants are growin ok , fish are alive.

quickest reply would be... if it ain't a problem, don't try to fix it. Fix it when you start having problems.

If you're looking to prevent any problems, the reality is you won't know you have problems unless you read/hear from someone else or it happens to you and you will have to figure it out when it does.

So, if you feel you haven't got problems, my recommendation is to leave it alone! Whether you do or not.. up to you

I have a cut IBC as garden bed, so 1.2 sqm surface area. Depth of media is 260mm, water cuts off about 50mm below media surface. System has operated for three years, no problem. I did add a swirl filter after year two, not because of any pressing need, just because it seemed the thing to do.

I agree entirely. And messing with a working system completely disrupts the current ecology: if you ARE going to do it you will need to carefully watch O2, NH3, etc.... and still might get overwhelmed by a sudden change in water quality. Don't mess with a working system!