Backyard Aquaponics
A place to discuss aquaponics

First things first - bloody terrific site
After I did a bit of reading, I thought I’d give this AP a go. Built an IBC system, 500 litre FT, 200 litre GB, shadeclothed FT, flood and drain GB, 80+ plants (seedlings & seeds), 20 rainbow trout (8-10cm) and 20 marron.
Looked so good, even the missus approved.
7 days AF (after fish) the plants looked fantastic, seedlings roaring ahead, even the seeds (that were accidentally spilled) in the GB all sprouted and were about 80mm high.
On the 8th day, all hell broke loose, fish dying, kids crying, ammonia through the roof….
After madly changing water several times a day (I read somewhere that dilution is the solution) for 3 days straight, 10 days AF all 20 trout have departed this life. On a brighter note, 19 of the marron look like they have decided to hang around for a bit.
Ammonia is still 2-ish, Nitrates and Nitrites still 0.
My new plan is to leave the marron until the ammonia and then the nitrates are down to zip. Then put in a more reasonable 10-12 trout. If the plants suddenly look sick from the lack of fish stuff, can I add some seasol (if so how much is safe). Any other tips would be greatly appreciated.
PS: I vow never to read any AP advice originating from Queensland ever again. WA forever!!!!

Oh dear....

This story is like a broken record here.

Good thing is your NOW in the right place and we can look at getting you back on track

Welcome to BYAP.

Even at 10-12 fish, I think you'll be a good chance of having a repeat event. A commonly described stock density is 1 fish per 20-25L of filtration in a mature system. If your only biofiltration is the 200L of GB, then you really only should be stocking 8-10 fish in a mature system. In the first season, you should reduce this by, say 25% i.e. 6-8 fish for 200L is a much safer level.

I've never kept yabbies or marron, so don't know how much ammonia and waste they generate, so just test the water for a few days and see what happens with only the shellfish in the system; you might have to reduce the fish numbers commensurate with the waste production from the marron.

Come summer time and you've harvested the trout, you can increase the numbers of fish to the "proper" level as the system will have matured and the bacteria fully colonised throughout the system.

As there are no fish now, this is a good opportunity to make sure things are "just right" before adding fish again. You can keep the system cycling with some Charlie Carp as a readily available and cheap source of ammonia with trace elements for the plants; about 10mL into 500L should raise the ammonia to about 1ppm, so use it carefully. If the marron are producing enough ammonia to keep the cycling going then you'll only need to add some trace elements for the plants, so Seasol is a good choice as it contains negligible ammonia; about 25-50mL of Seasol concentrate added weekly should keep things ticking along nicely. If the plants start to lighten in colour or show signs of nutrient deficiency, then you can up the rate.

Personally, I like to see a system "fully" cycled before adding fish; to have all ammonia completely converted and its corresponding nitrites completely converted (i.e. zero ammonia and zero nitrites) within 24 hours of the addition of the source ammonia. This is harder to measure with animals in the system constantly generating ammonia, but at this time of the year, full cycling can take up to 6 or 8 weeks, but if you do regular water test and keep accurate records you'll be able to see when it has happened.

Patience now pays rewards later, and it's a lot less stressful on you, the fish and the kids!

You haven't mentioned pH? This might be a good opportunity to add a pH buffer (shell grit or pure limestone) to the system so it's there for the inevitable pH drop when the cycling activity kicks into high gear?



Scott

Thanks a heap for the advice Scott....

pH is stable at around 7.4

So the current plan is:
1) Leave the marron toughing it out
2) Look for a cycled system by monitoring until ammonia and nitrites go to zip
2.5) In the meantime add seasol (because it does not have ammonia in it) when the plants look sick [25-50ml / 500l]
3) Test to see if the system is cycled by adding Charlie Carp (because it already has ammonia in it) [@10ml / 500l]
4) When the ammonia drops quickly (within 24 hrs) add fish [6-8] and keep watching
5) When all is stable, put away the test kit and bring out the beers when standing next to the AP....

Thanks again for this bloody terrific site....

20 marron in your system will produce more than enough ammonia to... not only cycle your system.... but probably power it alone... with the filtratrion capacity (grow bed)... you currently have...

You could add some seasol once a week or fortnite.... but don't add Charlie Carp.... you don't need another source of ammonia... you already have one....

Don't consider adding any more fish... until you add another grow bed... or two... or three...

Your nitrates suggest that you could add another grow bed immediately anyway....

You only need to add CC if the marron aren't producing ammonia.
Add the right number of fish cognisant of the marron in the system and the filtration you've got.
Don't forget to smile for the camera!

Also keep an eye on your PH, marron prefer it slightly on the alkaline side. A pH between 7.5 and 8.5 is ideal however marron can tolerate a pH of between 7.0 to 9.0. A pH of below 7.0 will increase the toxicity of dissolved metals within the water column and soften the exoskeleton of the marron.....causeing disease and/or death.

Make sure you have all pump lines and cables barricaded as they will escape, your poor water quality at the moment will also be driving them to the surface. High Ammonia levels are extremely toxic to them.

Optimum growth rates are between 17 - 24deg, any lower than 10deg they feed very little and or cease. Above 28 - 30deg and they will die. Now it is winter mine arent eating at all and Id expect your wont either. They only need to be fed twice a week in the summer months at around 3% of the combined body weight. With 500L IBC as a FT your water temps will swing vastly from day to night and will be difficult to manage.

Its important that crustaceans are stocked to m2 of floor space, I usually recomend about 7-10 yabbies per m2 and 4-8 marron per m2. Having said this I think you find it difficult to get 20 marron to grow out in an IBC. Ive got 10 in my 1500L FT which has a floor space of 2 m2.

Did you stock the tank to those densities straight from the getgo without cycling your media(bio filter)?

Or did you just forget to include that in your post?

I think you could find some bad AP advice in any state if you wanted to, but I'm glad i found this site before the others. Thanks Earthbound, your a legend

When I read 20 trout and 20 marron, with 200L of growbed I knew what was coming next. Thats more load than I have in an established system with 1400L of growbed and I can still get an ammonia spike if I feed heavily.

Keep going with the marron and see how it pans out, but think of getting more growbeds on the system soon.

Is that question for me tcshad

no, for the OP

OK - thanks for the advice and now for the new, new plan...
- Just leave the marron in the FT
- Seasol if the plants are looking sick

I cleaned my inside aquarium filter and threw the washings into the FT (aquarium fish have been healthy for years so hopefully no diseases and plenty of bacteria)

Jorgy - nothing personal against Banana Benders ay...just took some "1 fish per 10L" advice off another AP site that just happens to be based in your part of the world...

How long do marron normally take from 5-6cm to get to plate size?

To Bunsen, Charlie, Rupert and Mantis: thanks for the advice and better buy up shares in anything AP related - I think I'm hooked because despite my inability to keep fish alive for more than 10 days, I'm already measuring up for more FT and GB real estate....

!!!

Fish, especially trout are much more fun!



Scott

+1 bunson.

I have said many times before and will stand to this until proven otherwise....by my own experiments... that, yabbies/marron/gilgies/koonacs will only ever be an ADDITION to AP.

...and a great addition at that