Backyard Aquaponics
A place to discuss aquaponics

I have noticed that this part of Aquaponics seems to confuse many people early on.

The ratio of grow bed to fish tank. I will try and re-state here to help people get more comfortable with the ideas.

A grow bed to fish tank Ratio given as 1:1 or 2:1 would be grow bed:fish tank. If say you have two 500 l grow beds and one 1000 l fish tank you would have a 1:1 ratio. We are usually comparing the volume of the containers when we talk of this. If you had four 500 l grow beds and one 1000 l fish tank the ratio would be 2:1 grow bed:fish tank.

This usually brings up the next question, If I have a simple system and I flood the grow beds, how much water will be left in my fish tank for my fish? A quick rule of thumb is in a grow bed filled with gravel, the gravel takes up about 60% of the space and when flooded will hold around 40% water. This of course varies depending on the size of gravel and how much plant roots and solids are in the grow bed as well but it is a pretty good place to start.
So, If we have a system with 2-500 l grow beds filled with gavel, totaling 1000 l. It will take about 400 l of water to flood those grow beds. If the fish tank is 1000 l that will leave about 600 l of water in the fish tank. This usually works out ok so long as the system is not too heavily stocked with fish.

So what do you do if you want to stock lots and lots of fish in your 1000 l fish tank? This question usually brings up the 2:1 ratio and the need for a sump tank. You may also hear about CHIFT PIST (constant height in fish tank pump in sump tank) systems at this point in time. To stock heavily and avoid leaving the fish high and dry, most people use a sump tank to absorb the water level fluctuations needed to flood and drain the grow beds.

Lets use the 2:1 example with 4-500 l grow beds (total 2000 l of grow bed) and one 1000 l fish tank. To make this work as a heavily stocked CHIFT PIST flood and drain system, one would probably need a sump tank of at least 1000 l This way, even when all the grow beds are flooded, there is still a little bit of water in the sump tank and when the grow beds drain, the sump tank should not overflow.

I hope this helps clear up some confusion for people new to these ideas.

wicked....love this explanation, helps lots!

If I have like 2:1 ratio of GB:FT then I will need a sump to level out the water? is it possible to have a 2:1 ratio without having a sump tank to help out?
I mean if this is like 4 500L GB's : 1 1000L FT, with gravel taking up the 60% of GB volume then about 800L of the FT water is gonna be out of the FT and that's not a lot.

So has anyone achieved a system that has a 2:1 ratio without a sump helping the FT

No ...

Yes it is ... 800L out of 1000L... leaves you with 200L in the fish tank... hardly enough for a light fish density... let alone a higher density....

Lets assume you have stocked at 3kg/100L.... and your fish are 1kg each... you'd have 30 1kg fish in 200L of water....

Think of it this way.... a kilogram fish in less than a 10L bucket... reckon you might have trouble keeping them alive for more than ten minutes ...

No ....

... if I'm thinking small scale, I guess that'd be right Rupe, but hmmm... largescale? you wouldn't have to stock so high to keep a large system running, but then again you wouldn't be able to keep the water nutrient rich....

So does that means the closer to 1:1 a system is, the more diluted the nutrients are. The closer to 2:1 a system is with a sump helping out, you get stronger nutrients?
Following that if the sump water return to the FT is clear, mixes with the new dirty water, dilutes it so its back to the 1:1 light water anyway. so it doesn't matter whether you're got 1:1 without a sump or 2:1 with a sump! I dont have to change my system. (I dont have a sump )

I think the only time you only need to go 2:1 with an extra tank (sump) is when you want fingerlings or something that is not the same breed as your main fish or even just duckweed, which is not a bad notion unless you want them to suck out all the leftover nitrates

The growbed ratios are more to do with stocking densities and bio-filtration capacity Jensilaedi...

If you have more fish... or your fish grow larger... you feed them more... they produce more waste...

Your system needs to be able to process this waste... as it does so it produces the nutrients available to the plants...

More waste... more nutrients available to plants... potentially more plants...

That's the other benefit of 2:1.... you can have more plants... because you have more physical area of growbed... and you have more nutrient load... either because you have more fish (higher density) or you have more waste/nutrient load... or both...

The sump question is simply a matter of ensuring sufficient water in the system... particularly in the fish tank.... which is why many people have adopted the "chift pist" configuration...

A sump also provides some capacity for component failure... a backup reserve....

To clarify further Jensilaedi ... as long as you have sufficent bio-filtration... the system will always process the waste into a nutrient form available to plants... nitrates...

The available plants will take up the nitrates needed... if there isn't sufficient plants to take up all the nitrates, the remainder will stay in the system...

Uless you increase the number of plants, or the amount of uptake by the plant type/stage of growth (ie. tomatos are heavy feeders)... nitrates will, over time, increase...

This is usually not a problem, and the levels of nitrate required to pose a problem to your fish are extremely high... so high as to not really pose a problem as such...

Because you merely have to plant more to deal with it...

Conversly... if the number/type of plants and nutrient requirement exceeds the available level of that supplied by the waste provided... then you either add more fish... or feed more...

It's all a balance.... just follow the recommendations provided... it all works...

If you feel the need to experiment later... do so if you wish...

actually, there are many possible solutions:

say you have a 1000 l fish tank and 4 x 500 l growbeds and no sump
normally you would be left with only 200 l in the fish tank at the moment when all your growbeds are flooded

but who says your growbeds must be flooded at the same time?

if you would have 2 small pumps instead of one big one, timed alternately, each tubed to two growbeds
you would be left with 400 l in the fish tank

if you would have 4 small pumps instead of one big one, timed alternately, each tubed to one growbed
you would be left with 800 l in the fish tank

the advantages of such a system are not limited to the level in the fish tank:
-the number of pumps make it nearly foolproof
-you can adapt the frequency of flooding of the different growbeds to the type (or the growth stadium) of the plants in them

same goes for a system with sump:
for a 1000 l fish tank and 4 x 500 l growbeds you would normally need a 900-1000 l sump

but if you would have a sequencing system for either the flooding or the draining of the growbeds,
so that draining is never simultaneous, the sump can be limited to say 300 l

I would opt for a sequencing of the flooding, as that will give you the same control over flooding frequency

frank

Nobody Frank... it's taken as a "worse case scenario"... i.e that all growbeds are full at a moment in time..... for simplicity...



True... but adds extra cost... and if it assumes two pumps in the fish tank... in that case you'd also need another pump in the sump... unless gravity drained back to the tank...

In which case it is nearly impossible to determine the actual level...



Even more costly... and inefficient.... and 4 x times the likelyhood of a pump failure and a growbed going dry...



No it increases the possibility of failure... see above...

And adds to the possibilty of draining the fish tank if a growbed overflows/doesn't drain...



Not if the sump pump fails... and you have 4 pumps continue pumping from the fish tank... major point of failure...



So does the simplicity of "chift pist"... or flood & drain utilising a single pump in the fish tank to growbeds where flow is controlled by ball valves... and a sump/sump pump...

For someone concerned with "efficiency Frank.... I'm staggered at the suggestions...

And for the sake of simplicity.... why even bother...

For any "new" user... we recommend adopting a "simple" proven design for your first system...

Experimentation can come later when you've learned the basics... and if you really feel the desire to dabble...

please don't mix up the different propositions I make:

I first describe the "worst case scenario", which is when all growbeds drain at the same time

then I propose solutions to prevent this
because we can avoid it
that is what my post is all about

first proposition is without sump,
which automatically means you locate the pump(s) either in the fish tank or in the growbed(s), NOT in the nonexistent sump.

let's suppose the pump(s) is(are) in the fish tank (which I believe is the traditional way, and I would second that):
if the growbeds are then equipped with just a standpipe with a drain hole (smaller than the pump's output) at the bottom of it and an overflow, then timing the pump that leads to this particular growbed would be easy.
Exact timing would not be necessary: as long as the overflow level is reached, this would be OK.
frequency of flooding remains very possible.
locating the pumps in the growbeds is more problematic so I will not go into it.

it is quite obvious that 2 and 4 pumps are more costly than one.
but inefficient ??? why would that be ???
... please explain ...

.../...
where system security is concerned:
4 pumps each stand a chance of breaking down, which is obviously more than one pump, I will grant you that
this doesn't however increase the chance of a general system breakdown by a factor of 4.

quite the contrary:

The likelyhood of 4 pumps simultaneously breaking down would be (I estimate) 4^4 th = 256 times less than 1 pump breaking down, so you stand 256 times less the risk of losing your fish.

NOT 4 times more.

As for the plants: it takes a lot of time for a growbed to go dry
unless your media has no water holding capacities whatsoever.

If your growbed can't stand say 12 hours between floods (ample time to replace a pump, and MUCH more time than droughts can occur in nature), I believe one should reconsider their growing media (i.e. mix some media with water holding capacities with it).

even if you don't wish to do so this can be solved by keeping always a small film of water in the growbeds, which is almost natural: completely draining a growbed is difficult.

increasing the time between floods will coax your plants to grow deeper roots (a very well documented phenomenon) which will allow for stronger and healthier plants and limit the consequences of "a growbed going dry".

In this above described setup (with an overflow on each growbed standup pipe) the possibility of draining the fish tank is nonexistent (if need be I can explain further).

to summarize:
yes, 4 pumps will probably be more expensive than only one
but TMHO the many advantages by far outweigh that.

next: the sump tank variation does NOT include 4 pumps in the fish tank (don't mix up the solutions described).
please reread my post.
it incorporates a sequencer for flooding/draining the growbeds.

sure, a "one pump" system is simpler, but is it also "best"?
and even "cheaper"?
and more "reliable"?

let me I doubt it

don't forget: in a 1000 liter FT + 4 x 500 liter growbeds system and a "worst case scenario" without sump you are left with only 200 liter in the fish tank, and in a system with sump you need much more sump capacity = more footprint, higher cost.

even if the cost of a bigger sump is less than the costs of the extra pumps, you will miss all the other advantages.

we are not talking here of irresponsible experiments, as we are not touching any of the basic principles of AP.
(not even that of KISS)

only of very arguable alternatives which will enhance a system and make it more reliable

as shown above


frank

Exactly what I said...

Which means that you have to gravity drain your growbeds back to the fish tank... which means raising them above the fish tank or lowering the fish tank by digging it in...



Probably true Frank, and only differs slightly from the normally adopted, tried and tested method, where there are many holes drilled in the outer cover pipe and a single hole in the bottom of the standpipe... drainage begins immediately, overflows the standpipe, and continues after the timer ceases the pump through the bottom hole in the standpipe.

Setting the height of the standpipe correctly acts as the overflow... setting the timer to 15on/45off is suggested because many timers only have 15 min interval set points...

And 45 mins off has been shown to provide sufficient time to drain and sufficient oxygenation... but it assumes a sump concept with a pump (usually float activated) in the sump...



I hadn't even interpreted your design as actually involving pumps in the growbed... I'm not sure what possible benefit this concept would acheive... and it would take up further room in the growbed that could be utilised by plants...

Further you would then have to deal with the inevitable invasive roots blocking the pump(s)...



Four pumps means four times the electrical consumption... granted your could size the pumps down and possibly acheive the same or even slightly less consumption ...



If each bed is supplied by a single pump.... and a pump fails then you have a system breakdown... compromise the plants at the very least....

A single pump is perhaps just as likely to breakdown, and similarly compromise the system... but IMO is more likely to be recognised and acted upon... whereas 1 pump failure amongst 4 pumps may go un-noticed...



I never suggested that four pumps would breakdown simultaneously just raised the point about one...

but lets assume that to be the case... i.e that a power failure has occured for instance... with each bed fed by a pump.... how would you organise a backup system that could supply all four beds and maintain bio-filtration and oxygenation??



True the media will stay moist for some time... but remember that this is a constantly draining standpipe arrangement... and IMO it would be possible to not notice that one of the four pumps was inoperable... as the rest of the system would indicate that everything was operating as normal...




Incorporating an overflow (which you hadn't previously suggested ) would actually INCREASE the likelyhood of this occurring if a blockage occurred in a growbed drain as the fish tank pump(s) would continue to pump and overflow the growbed...

If the sump pump failed... as the pump... or 4 pumps would continue to feed to the growbeds and drain you would overflow the sump



Sorry but I can't really see any advantages at all...

And it would make harvesting your fish more difficult....



Sorry Frank if I mis-interpreted your idea... noted the point about "sequenced" growbeds, but nothing as to where the pumps would be located... assumed they would be in the fish tank as you didn't state otherwise... and everything suggested the pumps were in the fish tank...



Where would you locate them? in the sump??



"Best" ... there's no "set in stone" way to do things... but some ways have been proven to work, reliably... and to be easily implemented at minimal cost..

"Cheaper" .... noted that multiple pumps could be downsized and possibly consume less power and may be "individually" cheaper than a single pump...

But combined cost.... ??? ... then there's the additional costs involved with plumbed each growbed to each pump...

Cheaper... doubtful IMO...



Assumes a gravity feed growbed drainage... every other of your design options seems to suggest/incorporate a sump....



What advatages??



Never suggested the idea was an "irresponsible" experiment... doubt that any experiment (ethical anyway) is irresponsible...

Just suggested that as a new user ... it was perhaps best to start with proven, reliable design principles... and experiment later, if so desired ...



An assumption made by yourself... but not actually supported or verified by anyone to my knowledge... even yourself, to my knowledge have never actually built and operated such a system...

And anyway.... the thread is about "The Ratio question and sump tank tips." ....

Not about alternative design proposals....

And I'm sure this little ramble has totally defeated the purpose of the thread.... "clarification"... another successful hijack...

Jensilaedi,
Back to your questions.
Can you manage a 2:1 ratio without a sump. I believe it could be done using some indexing method (flout sequencer or something) multiple sequenced pumps or possibly even cascading the grow beds though this could have some major failure problems if not planned out very carefully. So yes it could be done but at the premium of complexity and the loss of the extra water buffer the sump tank provides.

As to the idea that nutrients are more concentrated in a system without a sump. Looking at things in this manor might be counter productive. Additional water in a system will act as a buffer and should be thought of as a good thing. The concentration of nutrients will reach a balance no matter the size of system or the amount of extra water. If you only have a few small fish and set up a 2:1 system with a big sump, you may find that you don't have enough nutrients for such system if heavily planted with greedy plants. The other side of that, if you have a very heavily stocked fish tank and a 1:1 system with no sump, you may have far more nutrients than you plants know what to do with and probably some water quality issues and solids clogging your grow beds. It is all a balance. If you want a system with a huge amount of water and only a few fish, it can still work, it just takes longer to build up enough nutrients to measure them. The balance is to have a healthy system which provides the produce you need and the amount of fish you want in the space you have available.

Example, I have a 10 gallon aquarium with one lonely little fish. That is hooked to 5-5 gallon buckets of gravel that flood and drain and two troughs with house plants. This system has a 55 gallon barrel as a sump. There are measurable nutrients in that system. In part probably because it is indoors and doesn't get as much light as might be needed to get the plants to really suck down the nitrates.

[quote="RupertofOZ"]Sorry but I can't really see any advantages at all...[quote]
why am I not surprised?

frank

thanks, TCLynx, for at least treating my suggestions as in line with your thread and worthy of consideration.

I agree with that, but mostly on the matter of temperature fluctuations
Where nutrients are concerned, as long as the biofilter function of the system is adequate, the buffering stays the same with less water as with more water
nutrients will simply be more or less concentrated, which you confirm:

It would be interesting if we could concoct a table of nutrient needs of plants.
I believe these data to exist.
that would make dimensioning and sequencing of growbeds flooding more adequate.
you could direct nutrients to plants in relation to their needs

frank

Given that the nutrients are in solution... how would you tailor specific plant nutrient requirements to specific plants or specific growbeds???