Backyard Aquaponics
A place to discuss aquaponics

and the fact that aquaponics stocking rates bear pretty much zero resemblance to aquarium stocking rates.

Well yeah. There's that, too.

I have made the comparison for people that if I were running my 570liters fish tank as a typical aquarium, I would have 6-8 tilapia in it. I have 40 right now.

The main difference being that my 300L indoor aquarium has about 20L of filtration media. Compared to 150L for my AP system.

It all comes down to filtration and how you remove the nitrates from the water, ie Growbeds or water changes.

Still, if you have accumulated fish waste on the floor of your tank, then it will start to diffuse into the water, and it will eventually build up to excessive levels. I think that the surface area of the tank rule not only has to do with how good your biofilter is, but the fact that fish waste goes directly down, and when it builds up, no matter how much you filter amonia, the nitrate levels will build up to levels that are intollerable for fish. I just don't think that plant roots are efficient enough to soak up all of the solluble nitrogen in the tank, no matter how much water is pumped through the filter. Roots are like our lungs, and the nutrients, (fish waste,) is diffused, or osmosised, and all of the excess nutrients are passed on through the system; just like our lungs, we don't breath out pure carbon dioxide with every breathof oxygen. I think it is better to have more tanks than excessive fish populations, becuase it is better for the whole system. Fish density is a bad thing; fish fight over food, territory, status, and so on. Stress is the biggest killer of fish, and population density is probably the biggest contributing factor.

Rampant, please don't take this the wrong way, but do a bit of reading in the various areas of the site and look at some of the members system.



I'll modify that to stress is the biggest killer of fish, and WATER QUALITY is probably the biggest contributing factor.

Dude, in short many people people running very high densities with appropriate plant levels Enjoy (sometimes too low) low nitrates, zero ammonia zero nitrites, high DO....................

I encourage you to build a system, ask questions people are more than willing to lend a hand.

Rampant, you are absolutely correct.... fish crap does sink... thats gravity for ya. I think you are getting mixed up. The fish waste is not nitrate, it does however break down along with any uneaten food into ammonia and other trace chemicals. The biofilters take care of all the ammonia and nitrite and provide us with usable nitrate. This nitrate is not toxic to fish in low concentrations. If you have ample plants... eg Jungles of tomatos... Then the nitrates are quickly consumed.

Fish will not fight over food under the correct conditions, because when you feed them 3 times a day with plenty of food then there is very few hungry mouths left over. You can't do that in an aquarium... the fish we use like SP, barra and trout will eat and eat and eat. Which is the whole point to intensive fish farming. We need to get as many fish to the table, in a short time and using a small space.

Don't forget too that most members would top up there tanks by about 50 -100 L a day if not more of fresh water, due to evaporation.

Believe me, we are not stocking anywhere near some commercial aquaculture companies.... they are only concerned by profit.

Rampant,
Many of us have arranged water flow and plumbing so that fish poo is drawn into the growbeds. Worms and bacteria break it down. There is not a thick layer of poo on the bottom of the tank. I measure my nitrates weekly right now because of some experiments I'm running. Nitrates are ranging as low as 5, but always between 10 and 40 with my current configuration. That's way better than any 'properly' stocked aquarium I ever had.

Higher fish density can actually be used to diffuse fish aggression. It is important to know what the particular fish that you have will tolerate. I find with my tilapia, a female holding eggs can get very aggressive, and would probably kill a tankmate if the two fish were the only ones in say, a 50gal tank. However, put those two fish in with 30 others in a 150gal tank, and her aggression is diffused among all other tankmates. Nobody gets hurt because she can't focus her aggression on any one fish for long.

Please do review some of our systems. You might be suprised!

I agree with all of you, I'm just coming from an aquarium background. As soon as I get all of the parts of my system running, I'm sure I'll ask more questions. I've been really impressed with most of the sytems I've seen on this site, and I'm impressed that there is threads for things specific, like strawberries, and system parts.

Sometimes it is better to start out in this as though you know nothing, with no prejudices. That way things don't have to make sense, you just do it because it is working well for others.

Good to have you on board Rampant

Hi JP, Is it a special kind of earthworm? I keep reading about worms that are actually living in the water. Do you have earthworms in your GB's?"

most of us use composting worms, i think there are three common types, red, tiger and african something or other............

earth worms till the soil, compost worms process waste.

There is nothing special about ANY type of worm living in water (or very wet situation) that has VERY HIGH O2. They breathe via O2 transport across their skin. The reason you see them "drowned" in puddles of water after a rain is because the puddle has very low O2.

I have worms - of the good type - lots of them - simple earth worms.

there often is a lot of emotion involved when people talk about fish (or other animals) density.
I find that many a "hard core" AP-er is horrified at the mere mentioning of the word "density".

we often forget that in nature lots fish live packed in very dense schools
like sheep in a flock: shoulder to shoulder
sheep have no problem whatsoever with that, as long as they have enough fresh air
same goes for fish: they have no problem with density as long as they have enough fresh water

I have visited a catfish farm in Holland that actually held 600 kg/m³
seen that with my own eyes
The fish were active, fed well and looked very healthy
this density eliminated cannibalism completely

I think we should talk rather of density/m³/hr:
It is easy to understand that fish living at say 100 kg/m³ with a (filtered) recirculation rate of 1 x / hr live in worse ambient conditions than fish at double density with a (filtered) recirculation rate of 3 x / hr.

Add to that that the higher water speed in the system will guarantee a much more efficient solids removal
removing the solids as quickly as possible fro the fish tank will avoid most DO issues in the fish tank
the higher water speed in the system will further enhance aeration

of course the biofilter must be able to cope with the nutrients to transform nitrites into nitrates

the delicate balance between fish density and growbeds volume or surface is the main drawback of AP:
in a pure AP system, you will grow a lot of vegetables for a small quantity of fish

that is why I suggested on another thread to add a settling tank and a worm bin between the fish tank and the growbeds
this will allow much more flexibility: the settlable solids can be either fed directly to the worms or redirected to the growbeds if your plants need more nutrients. You can even tap off some of these solids to feed to your ornamental plants in your garden or in the house.

this way you can actually balance the whole system out with regards to both fish density and plant needs / surface occupied (i.e. after partial harvesting of either plants or fish)
the worms are nice snacks for your fish, make for a more balanced diet and retransform waste into very valuable fish food
you can feed all scraps from your vegetables (and from your garden, and paper and cardboard) to the worms

the worm tea can be fed your ornamental plants in your garden or in the house or can be collected and stocked for later use when there are too few fish in the system compared to plants.
same for the worm compost.

even less waste.
win win win
isn't that what we are all concerned with?

frank

Thanks Steve. Going to try them too in my GB's when up and running.

i understand your logic in including the hr function frank, but the whole reason its not required is because of the growbed factor. if you stocked 4x the fish at 4x the turnover they's probably be just fine, BUT you'd end up having a net gain in nitrates unless you increased the growbed GROWING space so you had 4x the plants growing to extract the nutrients. hence if the everything is to a factor of 4 (fish, turnover AND plant number) they cancel out and make the hr function redundant.

If we were working on aquaculture alone where we would be dumping nutrient rich water then i may agree.

Just regarding the

i dont understand. the delicate balance IS the BASIS of AP.
what do you mean by "pure ap"? you will only grow the amount of veggies that the nitrogenous fish waste (governed by the amount of fish and feed) can supply