Backyard Aquaponics
A place to discuss aquaponics

I think the air-break should work, especially if the horizontal pipe is large.

I, too, was thinking about raising fish (tilapia) on duckweed. The ammonia from the fish would feed the duckweed which would go back to the fish. One would still need to feed some other food (or add fertilizer for the duckweed), but much of what is normally aquaculture waste would recycle into fish food. However, since 'ates can go very high without harming the fish, I decided to simply let the 'ates fluctuate and grow food for us instead. Tomatoes and summer squash SUCK nutrients, so there is never waste..

Ok cool so it looks like I might be predicting trouble where there is none. How high can nitrates go before there is an issue? I read everywhere they can go high but I'm finding it hard to find definite numbers for silver perch.

My test blue barrel system is nearly cycled so I'm getting nervous about getting everything just right for the fish.

thanks everyone for all the input.

-craig

I haven't heard anything specific for SP, but have heard that nitrates can get into the thousands range before giving problems with the fish.

Indeed, I've never been able to find any specific research regarding an upper limit for nitrates... not only for Silver Perch, but for most fish...

The only references I've found were for Blue Gill... which are supposedly limited to 450-500ppm...

Next time I'm out on the Murrumbidgee river, I'll take my test kit and do some nitrate readings to see where they sit in a natural environment (allbeit there may be some contamination from farm run off). I'd imagine the natural conditions fish have evolved under would have to provide the best/safest range.

Excellent, thanks.

I was thinking 80mg/l might be high.

I can relax

I took a test of the water in the river (the River Torrens) running through my front yard a month or so ago, just to see what the real world looked like and found ammonia 0, nitrites 0, nitrates between 5 and 10 . The water was flowing at the time, sometimes it isn't, so I guess the addition of fresh rainwater could change things quite a bit. Also there are fast growing algae aplenty in the river to take advantage of any nutrient so perhaps its pretty stable no matter what.
After all it is a few million years old so guess its cycled

-craig

A few days ago I put a second small grow bed onto my little blue barrel system. It was just a square plastic windowbox style pot. I had some strawberry runners and needed a home for them so collected some blue metal from the back yard and filled the pot with it and the plants. I suspended them in the FT (no fish yet) so that at high tide it would flood and at low would drain. My pH changed from 7.6 to 6 which I put down to the new media and the fact that I had almost cycled.

Today I discovered A white substance on the gravel near where I collected mine. I also noticed I could crumble the rocks in my fingers, and the white substance was powdered blue metal sitting next to the decaying rocks!

I'm guessing battery acid or something

So I just finished rinsing out my little system.

The bacteria was still working nicely but couldn't take the risk without a clean out. I did pH tests each time I filled and dumped the water and its now sitting at 7.2 (my house rainwater is 7.6 from the tap and the system was steady at 7.6 for the last month before my stuffup!)

How much of the nitrifying bacteria is in the water and how much will still be sitting on my scoria? I guess I find out tomorrow.

Dosing with ammonia to 2-3ppm.

I was looking at fish for early next week

-craig

Bummer!

The good news: the bacteria are almost entirely attached to the growbed gravel rather than suspended in the water, so you should be fine. But you'll find out in a day or so as ammonia converts.

Good luck!

Date 2010-05-01 2010-05-02
Temp 14 15
pH 6.8 6.8
Ammonia 0.25 0.25
Nitrites 1 1
Nitrates 7.5 160!!! (double checked)

NH* to ~2ppm

the test done on the 1st was done approx 2 hours after the clean out and after I added the ammonia (180 ml of 3 week old hummonia)

My rainwater tank water measures...

Ammonia 0
Nitrites 0
Nitrates 7.5

There seems to be something strange going on as these numbers don't seem to add up.

Would 3 week old hummonia be slow release ammonia? that might make more sense. And perhaps the plants shut down and switch to nitrites or something after their rinse stress . I would have expected a change in ammonia from yesterdays test though. (2 hours between adding the ammonia and testing yesterday would have seen a 300% water turnover so should have been well mixed)

Much stuff to learn!

Think whats happening just shows your system is basically cycled Bullwinkle...

Throwing the humonia at it... has resulted in it basically being completely converted to nitrates... hence your 160 reading....

Stop the humonia dosing...and whack some plants in there mate...

Probably time for some fish... if you already have some fish... definitely don't add any more humonia...

Humonia is urea which is slow release. It will not register on the ammonia test until it breaks down. At least some does break down in the aging process, but I'm not sure how much.

I think you have about 90 liters of water in that half blue barrel. So, 180ml of humonia in 90 liters is 2ppt or 2000ppm. If humonia is 1% ammonia or urea, you would be dosing to 20ppm!

I'd say you have a well cycled system. Wait until ammonia and nitrite drop below .25 and add some fish!

Date--------01/05/10----02/05/10----03/05/10
Temp ----------14-----------15-----------14
pH-------------6.8----------6.8-----------6.4
Ammonia------0.25---------0.25-----------0
Nitrites---------1-------------1-------------1
Nitrates--------7.5----------160-----------10

I've had plants in for a while



I'm still a bit worried about the fact that my pH is moving. I understand that the nitrogen cycle is acidifying (is that a word) but I have no idea how much it should change due to cycling.

I'm concerned that some of this lower pH is due to pollution.

-craig

Nah, looks about right to me.... you might want to mix some shellgrit into your growbeds now, so that the pH doesn't drop too much further...

started work on our second system


I might have to be away for the first few days of cycling the new system and thought these water garden slow release tablets might start me off. Can anyone see anything nasty in these?

2 not so shiny new GBs each measuring 1750 mm x 1100 mm x 300 mm

yay us!