Backyard Aquaponics
A place to discuss aquaponics

This is what they looked like just before they became dinner. My usually vegan daughter polished off one of the jade perch. Says she feels they had a good life and as humane a death as is possible... and were produced in a relatively environmentally safe way - though she is well aware that aquaponics is far from a closed system.

would be grateful for any thoughts from others who have had perch of mixed sizes in one tank... as per my post above (yes... this is also a bump).

Autumn is looming and nearly time for another order of jade perch fingerlings. Have been eating smoked perch fairly regularly... another 3 last night.

Will be moving the remaining medium sized perch (the runts of the last fingerling batches) to my sump tank so the new fingerings aren't bullied.

And so that those medium sized perch don't become its dinner, last night I also ate the very last murray cod - a lovely looking and healthy fish 1.68 kg and so close to 50 cm I'm sticking with that number. One of the fillets was prepared Peruvian ceviche style. I'm no chef... or Peruvian... but my mate is

Photos follow.

And for those interested, in the back right of the first photo is beef brisket cured with koji spores at 30 degrees C for a few days then aged and dried in a fridge for about a month. And the smallest cheese is ricotta cured for a month with koji - tastes a bit like parmesan but less salty. both of these were made by my mate though I contributed to the technical aspects of controlling temperature and humidity.

Lots of food with local provenance (as I believe the foodies call it) on that table - including aquaponic herbs/chili in the ceviche and rice salad and loaf of sourdough freshly baked but just out of shot.

should have sold the murray cod while still alive, people out west willing to pay big bikkies.

Yes... very sad what happened out west!

Beautiful fish ive got a dozen getting quite big cod

They look great... will upload a picture of a pencil case my daughter made me from the murray cod leather I've made.

Taste good too. But very slow growing compared to jade perch and I lost many of mine to cannabalism... I know there are techniques to manage but I don't have enough tanks (or maybe enough skill ). So that will be my last one

Double post... see below.

First post for a long time... have responded occasionally in other threads but not updated my own. Hard to believe it's more than two years.

The TLDR of below is:
* If growing algae to reduce nitrates, should I occasionally remove it to allow new growth
* will small jade perch choke on large pellets fed to their larger tankmates

My mature system is still producing good feeds of salad greens and herbs and the occasional plate of smoked jade perch... and the flowers are blooming too (will post some pictures later). But I have a couple of questions.

NITRATES and ALGAE "FARM"
I have had high nitrates from the very early days... well over 160 and probably as high as 400 at times. It's well documented on here that the fish (particularly fingerlings) might not like it and plants can be bitter and not grow well but until recently that wasn't my experience. But last summer and autumn I had trouble with my leafy greens for the first time... poor light might have had a part to play but I suspect nitrates. So I've decided to do something about it.

I have a 20 L bucket plumbed in to my system with an LED light on a timer. It works well in that the walls of the bucket are quickly covered in algae. But it's been going for a few weeks now but no reduction in nitrates. My total water volume is probably 1500 L and so turnover through the small bucket would be very slow. But I'm now wondering if I'm doing the right thing by occasionally cleaning the algae off the walls to let new growth come through (I clean the walls and drain the bucket so the algae isn't washed back in to the system).

JADE PERCH FINGERLINGS DYING
I've lost about 10 of 35 JP fingerlings in recent weeks. It's OK because I had too many anyway. But I'm not keen to lose more. In light of the above issue, it's tempting to blame nitrates. But I've had sky high levels before without any losses. The rest of the fish look healthy and are eating well. The dead ones didn't have any obvious disease.

My best guess is that the fingerlings are eating the larger pellets I feed to their more than plate sized tankmates and choking. The fingerlings are on 1 mm floating pellets... I could probably go to 2 mm. The big ones get 6 mm pellets. I try to feed the small pellets first so the fingerlings don't have a go at the bigger ones.

Does that sound likely?

First, it's good to hear from you again as the forum is a bit of a ghost town the past year-ish. I have a bit of catching up to do on your thread, it looks like I left off somewhere in 2017!

For your nitrates, my first suggestion is try planting something that draws nitrates heavily, like corn. Maybe you are overstocked for the fish to grow bed volume. Can you add a grow bed? It's interesting that you are growing the algae in buckets to keep it separate, as algae can cause water problems. It contributes to dissolved oxygen in the day, but uses oxygen at night / in the wee hours. So it can cause a DO crash in the early morning which may kill your fish. It also causes pH fluctuation for the same reason and could contribute to a pH crash also. That is my understanding, which is very limited and could be wrong. But algae is predominately a single-cell organism that will permeate your water, not cling to the sides of buckets - that sounds more like a moss or perhaps string algae - refer to the previous sentence, I probably don't know what I am talking about

For the fish deaths, yes fish can die because from oversize food. But typically that only happens if the pellet / object gets stuck in their mouth so they can't eat / breathe. If it makes it past the lips (fish lips??), then I do not believe it will cause a problem. So if the dead fish don't have a pellet stuck in their lips it probably was not the cause.

It could be low DO in the morning. Do you have a way to test the O2? Is your pH stable?

If you can't get the plants to use the nitrates, are partial water changes a good option?

FWIW those are my thoughts.

Thanks for going to so much effort to help me outdstjohn

yes... it's much quieter on here than it was when I joined way back in 2014. I still contribute now and then - to help beginners out with setup questions mostly. But the last time I posted on this thread was in 2019... immediately above yesterday's posts.

Good advice about the fish pellets possibly getting stuck in the lips... not the case for me so I have to go looking for another explanation for the fingerling deaths. I'm very confident it's not oxygen or pH swings. The system is very well oxygenated and the flow from the algae bucket is tiny... even if that water had zero oxygen, it would make an infinetesimal difference. And my pH is very stable/predictable depending on season and feeding rate.

As for the nitrates, you've nicely summarised the key strategies - less fish, less fish food, more plants or water changes. But I either already have, can't or don't want to use these for long term solutions.

I don't know enough about algae to tell you what sort I have but I'm confident it's not ordinary biofilm and it doesn't look filamentous... neither is it suspended... just a thick green growth on the walls of the bucket. For anyone interested, have a look at this threadhttp://www.backyardaquaponics.com ... hp?t=30164 Mr Damage (who knows a thing or two about aquaponics) recomended the strategy I'm testing. I've done some more investigation and it seems like it's popular in the aquarium community... they call it an algae scrubber.

Maybe I should have posted in that other thread... will do so if I get nothing here.

Here's a picture of my two growbeds... the things above them are two of my 10 native bee hives. The corn will soon be much taller and a couple of chilli plants will also provide some height which the smaller plants will crowd under. On top of that, the walls behind the growbeds will soon be covered with tomato vines and eggplants... I'm also testing passionfruit and dragonfruit. And the ground around the growbeds will soon be covered with cucamelon, sweet potato and nasturtim vines growing down from my growbeds. I really do get as many plants in my system as possible!