Backyard Aquaponics
A place to discuss aquaponics

Oh... and if he's going to breed Silvers... then he needs ponds, probably 4 x 0.5 acre...

And at least another full time employee... and a big shed... and....

As pointed out, it's still the same amount of feed between the two sizes, but wouldn't it be 10kg/day each? That's a lot of fish food, not to mention waste. In any event, I'm eager to see the results.

yeh i think we posted at the same time rupe . .

Yep - noone has gotten around ponds yet - still essential for early SP grow-out !

Freo hatchery here tried to do it all in RAS a couple of years back and couldn't get it to work.

Yep - 10kg food/day. thats alot of fish food!
2000*0.5=1000
1000*0.01=10kg

I reckon there is no way you can support that many fish as TC said, the "3kg of fish per 100 litres of growbed" rule, which was a maximum rather than a recommendation, goes out the window when your growbeds are that deep.

Those figures were premised on beds having 25-30cm of bed depth, so about 4 times the growing area of a 1m deep growbed. Lets not forget that ultimately it boils down to feed in Vs growing area ( No. of plants). Making beds deeper yet still trying to use the same formulas doesn't really work.

... sorry, moved the decimal point one too many places...

But the principle point stills remains the same...

Well, I don't know about that since I'm running deep grow beds and I'm dealing on a volume basis instead of the square meters of grow space. See different kinds of plants use different amounts of nutrients. Now OBO may find he is having high nitrates and that he will need to do something like add raft beds or something to make up for his deep grow beds but that is probably fairly easily managed.

Or a separate duckweed pond, to strip nitrates and provide a food source.

Yeah but that still adds up to "those levels of fish stocking, with the beds that are there ATM isn't going to work."

There has to be more nutrient removal or at least total solids removal from the system.

Yep, I remember Freo Tafe at the time, spruiking how they'd done it...

Didn't believe it at the time....

Better make that 2500km as I dont think there are any left for sale in WA this year.

I think that would be the trick if there is a problem with excess nutrient. He probably has the volume of grow bed necessary to convert his ammonia and nitrites, and would just maybe need the ability to strip out more nitrates. Then again, if he has mature and/or heavy feeding plants, then he may already have sufficient nitrate filtration with his current growing surface area.

Never had a nitrate reading yet.

I am quite happy with the whole nitrogen cycle being able to cope....I have run way overstocked systems before, and the conversion process is never the problem. It's always water clarity ie solids that become the difficult thing to control with high feed rates and low growbed capacity.

The feed rates quoted here are never going to happen...I will be growing the fish slower, mainly because it is an unmonitored system, and I dont want to push water quality too far. I also rarely have water temperatures in the optimum feeding zone for either Trout or Perch.

I accept the fact that I will be pushing the capacity of the system somewhat, but hopefully not too far.

No breeding will be happening in this system whatsoever.

I am running at about 1.5kg of feed per day at the moment, with 16,000 litres of grow bed.

So for the "grand plan" OBO... what fish are you going to run... Silvers, Trout... or a mix of both...

If you want 50-80 fish per week... you're either going to have to feed them at the rates quoted... or take longer to grow them out... which probably means having even more fish to meet the target...