Backyard Aquaponics
A place to discuss aquaponics

LB, i tipped in 3kg to my 1000lt tank.
However, i do not have ur fishload and i don't have ur plant load. Fish respire to produce CO2 and drag down pH. Plants give off CO2 outside sunshine/photosynthesis, dragging down pH.You cannot add too much shellgrit. Shellgrit will only buffer as it is required by the other elements in the system. If ur system is well buffered, the shellgrit will sit there until needed, i think. A higher pH, will mean fish grow faster, ammo is converted quicker and nitrite readings will be lower. I know u have had previous issues there, buffer away man, u won't hurt ur system and it costs peanuts.
Also per Janet's advice, should u decide to use a powder, potassium bicarb is better than sodium bicarb, as it buffers AND feeds nutes.

I have 28 pounds (12.7kg) of shell grit in my 570liter fishtank/570liter growbed system. I still have to add a little potassium bicarb each day to keep pH up.

That is interesting Janet, I have added <3kg of shellgrit in 2,500 litres of fish tank water and my pH sits steady on 7'ish - mind you, all my GBs haven't fully cycled yet nor is my main tank been in circulation very long either, maybe I should keep doing regular weekly checks

I wonder if the composition of gb rock has anything to do with pH buffering?

Absolutely it does! Everything has a bearing on everything else in AP. I have found that as my tank is all cement, my Ph stays up to around 7ish after 8 months of running. I have also placed cement blocks in the tank for the fish to hide in and that seems to help with the Ph as well.

However, at the beginning, PH was a real cause for concern for me becaus it was over 8.5! Fortunately the fish could tolerate it but it took longer to cycle and the some of the plants weren't overly excited about it. All is better now though.

Yeah, my pH sat sweetly at 7.4 for months. Then when I was complacent, it slowly slipped downward. Very sneaky.

I suspect that without the crushed coral I have, I would be adding even more potassium bicarb than I do.

Good night again last night.
Broad bush on desirable fish characteristics in recirc aquaculture. Bit of a case study on silvers v redfin, eg relative stocking densities, availability from hatcheries,growth characteristics, fcr, dietary requirements etc. Redfin=pest which i guess we know! Silvers tick all the boxes but aren't as sexy as murray cod or barra atm.

Interestingly, silvers being omnis will put on well over a kilo in 12 months in a dam environment. Bang a bale of hay in to get the small rotifers etc going, feed sporadically and bingo. Also have very high flesh recovery (40%) against say snapper (25%). Our lecturer lamented the fact that the whole omega 3 thing re:silvers has been a lost marketing opportunity so far. Lots of free potential health publicity there but everyone wants to grow barra and murray cod!

The Tafe is VERY keen to have a look at yellowtail kingfish, apparently growth rates are off the chart. They can't get any fingerlings. Anyone got any ideas?

Also mentioned that mulloway are far and away the best schooling fish in recirc.

For those using saline ground water, our lecturer is a BIG rap for Black Bream. A hardy, good schooling fish that hits the food and can handle suboptimal saline conditions.

Had a look at the mechanical side of things out the back. Big on mechanical filtration, drum filter, ozone filter, protein tower,then thru the bioballs and back out to the fishtanks. Using these methods, they can get 85kg of fish per cubic metre without pumping in artificial air-impressive.

Given that as APers we only tend to filter thru rock, it got me thinking that perhaps the smaller the rock size the better, better filtration of solids. With imagination, many of the larger mechanical filter setups can be readily done at home i reckon on a smaller scale. This is something i intend to explore further with my Tragic Greenhouse.

We have a field trip to a yabby setup in Anglesea in a week or so, should be good. Dasall.

Please post any info you have on them! I bought some from the supermarket the other day, granted it was pre-packages, but $39/Kg

hang on, aren't they salt water fish?

Yep, so are Mulloway......

Saltwater aquaponics anyone... mmm Mulloway. They grow fast too apparently....

but what plants would you grow ? salt bush ??

i guess you could feed it to other animals sheep fed on salt bush are supposed to be tasty

Kelp, live rock, corals..... You wouldn't eat the plants but the fish would be great...

There's a HUGE asian market for kelp and edible seaweeds in general....

Lots of research being done I believe.

SUSHI Farm