Backyard Aquaponics
A place to discuss aquaponics

G'day all

I had a great time with my first trout harvest, and despite a HSM event or three I got through OK. The most recent event was when I changed from CF to F&D and is detailed here (no need to really analyse it) viewtopic.php?f=1&t=13441

Sorry for the notepad style, I'm just reading this off my notes and readings.

Anyway, We enjoyed 6 (of 8 trout) on the 16th of September, and by the 30th of September the water was clear and I added a further 100-150L to increase the water level up to the 600-700l mark.
2nd of October saw the final two meet their fate and the large cauli & broccoli removed and seedlings put it. Next readings were 13th October (after a week away) where the water was exposed to excess sunlight resulting in green water... not my fault as I was away. On the 15th I added 11x fingerling barramundi (and yes, I'm waiting for the rants ) and took more readings today, which all are OK.

readings wise,
* Ammonia has been <1 since 31st August, and generally around the 0.5 mark. It peaked at 1.0 with the green water, but this has since dropped to the normal 0.5.
* Nitrate was 160 with 8 trout (19 Sep), 20 with 2 (2 Oct), and since dropped to 0.
* Nitrite is generally 0-0.25, and been 0 since the 6 trout were harvested.
* pH was 6.8 up to 19 Sep, which it jumped to 7.4... Having said that, there was a week of solid rain and I imagine the natural rain would have contributed to this. It has since been around 7.4-7.6 since 19 Sep.

* Temps: have been a steady 20+ degrees (and last readings tonight was 21.7), and I have installed a 300W heater just in case for the cold nights and days that we might have between now and full summer time.
* Fish: I've had 9 marron in there with no problems, and I'm the new proud owner of 11x 10-13cm barramundi Having said that, I've fed them once (Day 2), checked back and the ~15x 3mm feed pellets I threw in earlier were uneaten on the surface.
* Plants: I removed 10 large cauli & broccoli, kept the 4 biggest, and the space was filled in with two advanced tomato plants, and a variety of seedlings.
* Pumping & Heating: Been running on CF ever since the HSM noted above, no problems noted with the pump system. Bought and installed a heater 'just in case'.

So the questions (and reassurance) that I'm seeking,
a) are the 11 barramundi OK in 20+ degree water, even though I can't see them through the murky water?
b) would the readings (and the green water) indicate that adding that extra water have caused my systems bacteria to reduce in number (or even back to nothing?)
c) Question for Mr Damage & Charlie, and other crustacean fans; would the marron have caused enough ammonia production to keep the nitrogen cycle going?
d) which is the lesser of two evils - remove 200L of the green water and replace with fresh water, or keep the water as it is and let it clear up naturally (could I add egg whites?)

Thanks for your comments again

Deano

PS: oh just adding, I'm not feeding due to the green water. Good idea??

If in doubt, not feeding is generally the best plan.

Block the light from the water to deal with the algae.
Get as much algae pumped to the grow beds as possible (decomposing algae in the grow bed can help reduce future algae blooms, topping up water may have contributed to the bloom but changing water now will probably only exasperate it.)

the egg is for getting suspended particles to drop, I don't think it will work the same on algae. Block the light from the water to deal with algae.

The pH. You might check the pH at dawn and again late afternoon and see if there is a difference. Algae could be causing your pH to have a diurnal swing. I wouldn't mess with the pH, only check so you know what's going on. Algae blooms as water starts to warm up can be quite common.
Block the light from the water, that is the best way to get rid of an algae bloom.

Have you added any salt to your fish tank water yet?

It is a good idea to do that.

Wack in a barrel filter like mine, it will filter out the suspended algae in probably 4 or 5 days..

Yeah Zubin, I added 3 ppt of salt when I had the trout, the marron didn't seem to mind it at all.

When I got the barra off the supplier, I added two cups into the 15-20l of water and dosed the tank afterwards once they'd settled. Without having a salt measurer (refractometer?), I'm not sure how strong it is - but I can always add more if need be.

Thanks for the idea of the barrel filter, I'll check it out

Absolutely...

When I first built my kids little blue barrel system (50L of gravel and 70-80L of water), they didn't want fish, they wanted yabbies!... so we ran it it for about the first 6 months on 6 yabbies and we had excellent results, the plant growth was great.

Their feeding and nutrient output slowed when the temps cooled down and the plant growth slowed, but in saying that, they still fed just nowhere near as much... so they still would've been producing some Ammonia.

Even when they aren't actively feeding, fish and crustaceans are still giving off Ammonia and it wouldn't take much to keep your bacteria colony idling along.

+1 for Dr D

to you Mr Damage & Charlie

While I've got your fine attention, I haven't been actively feeding the marron as such - from memory they don't eat all that much and feeding sparingly is better than over-feeding?

Speaking of which, what IS the acceptable feed rate for say 9x 100g marron? (I know that as I bought 10 at 1kg!) I wouldn't think all that much, surely? I guess they'd live off the scraps that the fish leave behind or sink to the bottom?

Thanks again - you guys rock!!

Dean

Generally if in doubt, feed less.

But you can also let your water tests be a guide. If you are seeing ammonia or nitrite much above a trace, then you should probably be feeding less. If your ammonia and nitrite are both 0 and the critters seem hungry you might get away with feeding more.