Backyard Aquaponics
A place to discuss aquaponics

It's easy to type without giving an impression of anger, just type the same keys, but do it softly and gently.. hehe (I hope this was inferred as a joke, as it is meant to be)

Ok this is important ! I am not challenging the beauty of F&D! I love it and will stick to it till my death. (unless someone invents a better one).
Why did I start this thread then? Here is the story...

OK Gokul... think I get where you're going now.... but still don't get the point...

eg.... take a half blue drum.... filled with 100ltr of "seemingly" round clay balls... in actual fact they're somewhat porous and definitely rough and pitted....

But assuming they are round and smooth.... if a thin film of water coats each one... then the total area available to the bacteria to colonise is still vast surely..... ie surface area of a sphere x no of clay balls.... a significant total area.....

Alright, assume your arguement that the nitrification is taking place within that thin film....

My contention would be that in a flood and drain system.... that film will ...

(1) never dry out completely....
(2) be readily and almost continually refreshed....

Remember, for most using siphons and continuous pumping, the growbeds are constantly being refreshed with water... even as they siphon.... essentially it is almost "continuous flow"

With a "continous flow" system as defined (VB) then obviously this is constantly the case and as such in reality the arguement is null and void....

Maybe it has some validity in systems operated by timer cycles.... theoretically the thin film could either dry or not be refreshed by "flood" for a period of time.....

But so what????? .... the area of bacteria is still huge..... and it works

Ok , the story is like this. (will answer Rupert's post next)
I have a 50 litre micro system that I struggled to get to work for 4 months, and only now it seems to be picking up speed. I learnt a lot(from you people mainly of course!).

It so happens that my growbed to fishtank volume ratio is a really low 1:4 (nearly).
So, now and again I used to get ammonia/nitrite spikes (I don't have a test kit, hard to find in Indian LFS. Used my nose to smell fishy smell of ammonia or the fresh rain smell of a good system. Also I have spent months watching my fish behaviour like an idiot moth stuck to a lamp.)

(Also notice I haven't put up a thread about my system, cause (1) no digital camera (can borrow from cousin though) (2) no test kit to help you people solve my problems (3) I'm embarrassed about my system (not working until just a week ago) . But shortly I WILL be putting up a thread, don't worry!)

So with the low growbed volume, I used to get ammonia smells and bad fish behaviour and plant growth stalls. But Steve has always said there is always enough surface area for bacteria, and that the growbed volume was mainly to help with solids.
When I dug through I found no cloggy solids, besides my system was new, chances of it clogging so fast are low.
So I thought, if there was enough surface area, what could be the problem?

Humm ... ok.. but most of us aim to turn over the total volume of the fish tank at least once per hour..... so???

Are you suggesting that this might not be sufficient.... or is it more that you think that such a turnover is inherently "inefficient"??

Is there a better way in your opinion?

gokul,

dont take this the wrong way, mate.

sometimes we can get an idea stuck in our head so firmly that we are blind to other things. i love this quote "when the only tool in your shed is a hammer EVERYTHING starts looking like a nail"

I'll tell you something that may surprise you. i have been running my system for the last 4 years on an approximate ratio of 1:5

zero ammonia, zero nitrites, big plant growth.

a 1000L tank and a bathtub. i have harvested 22 trout at upto 750g, many jade perch and some silvers....................

Trust me when i tell you that colonising space for the bacteria is NOT the issue.

Also trust me when i say that you should not muy one more thing till you get a test kit. i have had water that has killed fish (test systems) with 4 to 8 ppm ammonia and "smelled" fine.

lets start from scratch. throw out the theories for now, explain EXACTLY your system, leave NOTHING out.

Steve

Maybe no real problem Gokul.... if your systems only 4 weeks old... but now showing a marked pickup and ability to process...

Then it's probably just "cycled"... i.e it's now at a point where the bacteria are growing/processing the available input.....

With a low ratio.... then depending on number of fish and how much you feed, or how much you vary your feed ...

Then it's more than likely you will get spikes.... especially until you're fully cycled....

When you are the bacteria will expand to match (or at least attempt to match) your feed input and fish output

Obviously there's a limit.... hence the suggested ratios fish:growbed volume....

I typed this before Steve's and Rupert's posts, I will submit this anyway to complete it:

So what is the problem? It may be that the bacteria are all there, but they're not getting enough water to process with a low growbed volume, after the draining is done.
So increase the cycle rate, or make it totally continuous. (I don't like continuous though).

I do agree with this comment in general and have processed very large amounts of crap with realtively small ratios (because as we know - the 2:1 ratio - which is relative to so many variables anyway - is largely based on what is needed to process the nitrate, not the ammonia and nitrite). I must comment though that my hydroton bed has proven to process the nutes much worse than I would have expected. Even after a few months of operation, it was still only coping with about 110 grams of feed a day (this is a 500 litre bed running rapid F&D with autosiphon). I did better with my 500 litres of drainage gravel.

No the thought was: why do aquaculture or aquariums get away with small volume of filters (essentially continuous flow, running all the time), while F&D needs a really large volume?
(oh wait now -- aquaculturists/aquarium people do have to clean up their clogged filters periodically! We don't (F&D AP) ! I take bacb that arguement then.)

That's great to hear!
Ok. I will do this on Saturday (am preparing for a test now, will last for the next three days).

Thanks people!

(Why do I use 'people' - when I use 'guys' I realize there are also gals so. The phrase 'guys/gals' is too long.)

I'm feeling very good now. I can carry on with my system with 1:4 ratio!
You're all a great help.

hmmm....
I will describe my system on Saturday and we can see what the real problem could have been (seems to be picking up now though... must have been a combination of overfeed and things like that. Psst: the plant growth had also stalled for 1 month or so! It must have been the aquatic plants (hydrilla weed) that was sucking nutes. I removed the mass of weeds and plants started to graw again. But why the fish deaths and bad smell before? We'll see on Saturday, have to prepare for test.)

Hi Gokul:

I think I know what you're saying, you are saying that the bacteria live on a thin film on the gravel, and that since the gravel is drained more often than flooded that most of the time the bacteria have a water volume to process that is only as big as this film. So the bacteria is processing one film volume per hour, right?

If the bacteria can process this water film in less than 45 minutes then the biofilter is not being used to its potential - it could be flooded and drained more often, to the point where the bacteria cannot process the water film fast enough before the next flood event. This all assumes that you are only concerned about the gravel as a biofilter alone, and ignoring the needs of the plants. BTW, I have gravel beds that are only used as biofilters so I don't find this train of thought that unusual.

Assuming a sphere is perfectly reasonable for these calculations, how else would you do it?

It might be a good experiment to see how fast a given amount of ammonia is processed down to zero ammonia and zero nitrites. Using this number you could optimize the flood and drain period, either slower or faster. Either to figure out a good guess at volume for a new system or just to satisfy curiosity.

The gist is that when in doubt add more gravel.

Bad smells from your system may be insufficient oxygen levels. Add more aeration or speed up the flows.

Steve and Rope are kind of easily tweaked about gravel lately because it seems a lot of new people are throwing aquaculture and aquarium tech at the problem. The thing to keep in mind is that for our purposes if your gravel beds are large enough and you water is flowing at a good turnover rate that you will not need any further technology.

HTH!

Ah! You are my saviour! I fall at your feet. You have understood me completely!! yesss!

I am not trying to do it another way (at least not now). What I am doing is simply justifying the need for such large growbeds. And trying to explain my insights into how it all works inside the growbed.