Backyard Aquaponics
A place to discuss aquaponics

I personally prefer to have 1:1 purely for safety and more stabilized water

I have a 10,000 ltrsump and 2 x 5000Ltr Fish tanks so when the water comes out of the fish tanks the sump kicks in and sends more back less fluctuation in water levels in the fish tank...

There is a big danger to having more fish tank than grow beds. That is it encourages people to add more fish and when you have bigger fish tank than you have grow beds, you don't have enough filtration to support a larger fish load!!!!!!!!!!!

I like twice as much grow bed as you have fish tank as this gives you enough filtration to support as many fish as will survive with only atmospheric aeration (no oxygen injection) provided you have ample pumping and flow through the fish tank. Granted if you do stock that heavily, you don't have as much stability or buffer on the system but having more grow beds does not reduce system stability it is having too many fish that does that. If you are worried about temperature stability and flood and drain grow beds then run them constant flood and they won't cause the temperatures to fluctuate nor the water levels but you must make sure there is plenty of aeration and flow through them to avoid anaerobic spots.

I've been running different combinations. I have one bed that runs constant flood just because I have no good way to make it flood and drain and it's been doing great other than the banana that broke that bed last summer. I have some small constant flood bins that are growing water chestnuts in summer and watercress in winter, that is great. I've got two auto siphons still working on my big system. Most of the beds are essentially timed flood and drain with the indexing valve but I also have a flout that does timed flood and drain with three beds. I must say that most of the plants do seem to like the timed flood and drain best and they are doing even better this spring with my lower nutrient levels and more mature system.

That hydroponic idea that flood and drain leaves the plants starved for nutrients between flood cycles must be using fairly sterile media. I don't have any plants showing major signs of deficiencies in the flood and drain beds more than the constant flood beds and actually the plants in the constant flow pipes and rafts seem to be showing the nutrient deficiency the most so you are not selling me on the idea that the plants suck up all the nutrients in the drained bed and are lacking in less than an hour and suffering for it. Heck I've got some beds that only get flooded once every six hours and they are not showing any more nutrient deficiency than my constant flood bed.

However, I do see where the constant flood gets the bio-filter going faster and is more stable for temperature.

Regarding GB:FT ratio, maybe it's better to talk GB grow area to FT volume. If you have large volume GBs with low grow area then you should be fine temperature wise. But in my case i have small volume GBs with a fairly big grow area if you compare it to it's volume, and when the sun hits the growbeds they warm up the water pretty quickly.

When i started my project i had 1600 L of GB and 1000 L of FT and the system was really unstable, had good filtering capacity but the temperatures were fluctating like crazy, specially when i introduced the auto syphons. For stocking rates i use 1m2 of green leaf area to 1kg of fish or 100g of fish food.

I also support the theory of bigger FT because you give more space for the fish to move in, as long as you'r not too curageous with stocking (as i was), it's better to start with low stocking and then move on step by step. For instance i stocked my 1000 L FT with 50 kg of fish (i calculated 20 L of FT water for 1kg of fish--yeah right), but forgot to put into the equasion how much grow bed space i actually had (only 8,8 m2 if i fully plant it with seedlings in the start) which resulted in a lot of dead fish and a really bad bad feeling in my guts.

As far as my experience goes with constant flow the problems arise when you don't have enough flow in the GB (lack of oxygen - as TClynx said) which is pretty common in square GBs and dead spots appear specialy in the corners. I used to run Deep water culture (no grow medium, just roots floating in the water) hydroponic system and it was quite a challange not to suffocate those roots, you would need even higher flows with media present, since it obscures the flow.

1kg of fish for 1m2 GLA (green leaf area) which means 1m2 covered with healthy growing plants no less no more.

If you don't use a prefilter i would definetly go with flood and drain, else i'd go with DWC and large volumes of water.

Hope i'm not pouring even more confusion in this debate and your decisions

Seems a little light on Molj... We have systems with much higher stocking levels than this with no problems. That would translate to 4 fish in one of our courtyard systems with a 2sqm bed, we have about 5 times that amount of fish.

There's an other way to work this stuff that seems to be ignored. (that could be because there is something wrong with it but I cant see any issues.

I think it was TC who wrote about it ages ago...
if you put a grow bed above the sump as per usual, and then add a second grow bed so that the bottom of the second GB is at the same height as the water in the sump when the top GB is full, the second grow bed adds to the sump water rather than subtracts.

perhaps better described with a picture...

http://backyardaquaponics.com/forum/dow ... p?id=22394

TC said she couldn't remember what user this came from but is in the section "Useful aquaponics diagrams"

viewtopic.php?f=11&t=5311&start=30&st=0&sk=t&sd=a

or my animation that is too big to fit on this forum (is there a way around the 2 meg limit? )

http://120thingsin20years.blogspot.com/ ... ystem.html

I am only going to be able to fit 3 beds in the area of this system so will try timed flood and drain.
Q. what size standpipes for the 500L beds, I am thinking 32mm and will try 15on45off. Also what size hole in the standpipe and is there only one hole or more
Sorry for the dumb questions but havent tried timed FD before

I use 40mm for 1000 litre beds, and thats plenty for around 4000 lph flow per bed.

just a thought...

I drilled a few smaller holes in my standpipe. Then I cut a short 2 inch section of standpipe and split it lengthways. This allows me to slide the short section over the standpipe to partially block some holes in the standpipe making it adjustable. It worked a treat.

Thanks guys, so I reckon 32mm should be fine, and thats a great idea BW

Hm, so you'r saying you have 5kg of fish per m2? Sounds like a big pile of poo for 2m2 of grow beds, do u use worms for processing that? Another thing is that i use lime gravel for my growbeds, which stunns the plant growth (Fe uptake is restricted with high concentrations of CaCO3) had problems with that from the beginning (Fe deficiency), definetly one of the negative factors in my system. The other one is that i don't have air pumping in the FT, the water only get's oxygen from mixing (syphons + water pump).

Have always feared the day that i'll have to replace all the gravel with something more inert, my back hurts just from thinking on that

I should run some nitrogen tests on my system and weigh my carps(haven't done that for almost 2 years now, and they got pretty big

But i'm quite positive on the ratio 100g of fish food per m2 per day, can you confirm that?

sorry for hijacking your thread Mantis, i'll finish ASAP!

Can someone drop everything in this thread in bullet point form or something. I'm really lost

GLA? sounds like a non-denominational video game enemy. http://www.acronymfinder.com/Global-Lib ... my-(gaming)-(GLA).html

My GLA extends as far as my pumpkin can.

gla as molj is talking about is green leaf area, that is, the surface area of his growbeds.. probably based on a hydroponic model, as molj's nutrient input is based on the volume of his fish food..

the way that we are used to looking at it or talking about it is total volume of the growbeds, and equating that to the total fish tank volume, straight up liters to liters or gallons to gallons, not surface area..

Yes Volume of filtration is what we talk about in AP eh. Green leaf area means nothing IMO as all we need is enough plants to soak up the nitrates.
Volume of grow bed media for nitrification and plants to soak up the resulting nitrates
I am guessing that one tomato plant would soak up the nitrates from 20 fish

yea the GLA or the surface area to grams of fish feed method is more related to floating raft systems where solids are removed and there is separate bio-filtration. That is the UVI method and if you try to use the UVI numbers for a media based system you are likely to run into issues since the pieces parts are not fully interchangeable. The raft method has things like needing air stones in the grow beds and the flow rate through the rafts per minute and such as well as the fact the solids are removed. And if you don't remove the solids you wind up having to do super low density systems like the Friendlies low density system which you might have 20 fish in a 1000 liter tank with two 4' by 8' rafts.

Anyway, when you start looking at media based systems the rules are a bit different and I personally don't believe that the surface area of the grow beds is the most important factor the way Dr Lennard's calculations say. According to his notes I should have had to re wash all my gravel for my big system at least 12 times by now to avoid problems and I have way to little surface area because my grow beds are deep. It seems rather simple for me to figure I want twice as much grave as I have fish tank and then stock 1 fish per 5 gallons for the small types of fish or 1 fish per 10 gallons for my monster catfish. This works very well provided you don't pollute the system with over feeding incidents (malfunction on an auto feeder or being away for a big weather change, automatic feeders are dangerous.)

As to media being a problem, well it all depends on the type of gravel you get. If you used limestone or marble gravel, yea, that will be a huge problem. Quartz kinds of river gravel are great. There are many other types of gravel or lava rock which work great. Just test the gravel before you fill up the system. Simply ordering pea gravel doesn't tell them what type of rock and around where I live, the cheapest gravel is going to be limestone and that doesn't work well for aquaponics. I've got one system with just brown river pebbles as media and the pH in that system will fall if I don't buffer it. This time of year it's getting buffered by the well water when I top up the system.

I think that a system with an IBC as fish tank and an IBC as sump tank and then two IBCs cut into 4 grow beds would work just fine as a standard timed flood and drain. If you find that the water level in the sump is falling too low, adjust the stand pipes or water level in the grow beds. Always make the stand pipes removable so you can make adjustments to them. You might even put the holes several inches up the stand pip so that the very bottom of the beds don't drain and that might keep the water level fluctuations from being a problem at all.

However, having a bed or two as constant flood with a small pump running them all the time could also give some constant flow and aeration and some plants prefer constant flood so I'm not against such things and it would also help get the bio-filter up and stable faster.

it's all good