Backyard Aquaponics
A place to discuss aquaponics

Hi guys
To me there seems to be some mis-conceptions about feeding. I do know much about the plant side of aquaponics but I do know about fresh water fish especially Silver Perch as what I have learnt on my farm. To be successful in growing Silvers and other fresh water fish there a a few basics you need to know.
1. Ammonia (ionised and compound (un-ionised), Nitrite and Nitrate.
2. Two bugs. One that converts Ammonia to Nitrite and another that coverts Nitrite to Nitrate.
Ammonia has the two forms 'compound' which is deadly to fish and ionised which does not effect fish. The ratio of one to the other depends on the pH. A pH of say 9 produces a VERY high percentage is compound (deadly) ammonia while at a pH of 7 the ammonia is predominately ionised ammonia, safer for fish. Water temperature will also affect the ammonia ratio but to a far lesser extent.
Fish, fish poo and old feed produce ammonia. You need ammonia to promote the bug growth which in turn eat more ammonia.
The down side of the ammonia eating bugs is the create nitrite which is also deadly to fish. Here we need another bug to grow that eats nitrite and creates nitrate (safe for fish at reasonable levels) .
A balance system is when ammonia produced by fish and feed etc = enough bugs to convert ammonia to nitrite = enough bugs to convert nitrite to nitrate.
Problem is you need to force a balanced system without killing fish.
To get this right you need an ammonia test kit and a nitrite test kit.
A very important point is that you need to create an unbalance system to let nature balance your forced unbalance by growing bugs.
The ammonia test gives you a total ammonia result. A I say previously you need ammonia to grow bugs so additionally you MUST keep the pH at around 6.8 to 7.2 for safe ammonia. When ammonia bugs are created and eat the ammonia you start the nitrite problem. Here normally I use salt to help protect the fish but within an aquaponics system this may harm the plant life (could someone help here). Alternatively, you could do some water exchange (fresh rain water) to limit nitrite levels. Tap water has chloride

This is becoming a little long winded but a couple of very important concepts to remember.
There is always ammonia and nitrite in a well balance system but you have enough bugs to keep the balance the system. A test kit reports an excess of ammonia or nitrite in the system where the balance exceeds the bug count.
A really good way to get a new system in balance is to leave the fish out and use cloudy ammonia to force a system into balance (saves the dead fish). This can take 6 weeks depending on water temperature. I actually add cloudy ammonia to by systems if I have removed the fish to keep the system "alive" with bugs.

JA, thanks for taking the time!

Its always good to have this info re-posted so people can really get their head around it, i have posted an ammonia/ph/temp chart in the useful info section as well as ammonia/ammonium nitrite and ph info, but i'm not sure how many people take the time to read it.

I guess the thing with "months to plate size" seriously depends on fingerling size at purchase! The last batch i got were the smallest ever, and they are certainly taking their time in growing compared to the "large" ones i've had before.

Saged advice from someone in the fish biz is always welcome.

interestingly enough the calcium carbonate that most of us are now using to buffer their system seems ideal as it tends to buffer to 7.2 with no risk of over-shoot and is self regulating without having to continuously check ph.

Cheers

Steve

Very clear explaination, JA. Thank you.

Interestingly, my pH has dropped below 7.2 in spite of the 28 pounds of crushed coral in my growbeds. I didn't think that was possible with so much of the stuff. I'm running about 6.8 now.

6.8pH is OK with Silvers. Certainly eliminate any risk of ammonia problems. But warning I have found that some ammonia test kits will give an apparent high reading of the pH is too low in the area of 6.2 and down
From my perspective I use Calcium Carbonate (bicarb soda) for two reasons.
1. To increase the pH if I’ve had an acid drop, and
2. To maintain the total alkalinity hardness which will stabilise the pH
Calcium Carbonate has a natural pH of mid 7’s (7.6 it think) cant remember the exact number so therefore you really cant overdose on it.
I did have a problem once where I was trying to age my water (get the ammonia bugs to grow) and I had fish in the pool of 10,000 litres. As I was running high ammonia to get the bugs to grow I had to keep the pH low <7.0. As I had a lot of alkalinity in the water I was adding 1 litre of HCL every day to keep the pH down as the high alkalinity dept driving it back up. When the bugs did grow I let the pH settle to where it wanted to at 7.5
Carbonated hardness of 70 to 150ppm in fine for Silvers

I hate to rain on the high pH brigade, but my system is still sitting down at around, or just over 6. I've added garden lime, shells and limestone rocks in an attempt to try and raise the pH to a more "acceptable" level just recently, but it made little difference, so I left it...

Now I know all of the literature and common knowledge of aquaculture and the chemistry behind it says that this is bad, and this is why I made a concerded effort to raise my pH, (for a week or two) . But at the end of the day, the silvers are eating well, the plants are all growing well, and the system is flourishing..

Perhaps it's the maturity of the system (3 years), I don't know. But while everything is ticking along nicely I'm not going to try and play with it too much. I'll add a little more shell grit now and then as I remember but I don't see any reason to wage a war on my pH if everything is working..

Anyone have any idea why this would be so, why my system is stable and performing well at such a low pH?

Damn, just lost a half page post! CBF posting it all again.

basically said that maybe quantity of bac is making up for lost bac. efficiency

Also stated that at ph 6.5 and temp of 20C 16ppm ammonia would seem acceptable from the table in the useful info section. where as at ph 7.5 its around 1ppm

Don't you hate that.....

Hey, I'm just happy it's working.. I'm running at ok stocking levels, still got about 110 SP at around 380-400g average, in a fish tank that averages about 1700-1800L..

But I would be interested to know why it goes against most of the commonly held ideals..

I'll do a full set of tests tomorrow and post em in my thread...

i bet your ammonia is "high" but that its well within limits for the PH. worst thing you could do is raise the ph with that ammonia.

worst case is that you're not getting as many nitrates as you could, but i suspect you're happy enough with the growth LOL

Got to agree if your system is working dont screw with it. I know the book say 7.5 is ideal but I know of farm that deliberately grew VERY high stocking densities for thousands of fish at 6pH as they could not control ammonia.
How do you measure your pH???. I have used expensive and cheap probes/digital meters and the good old pool droplet test kit and I really find the test kit the best (and cheapest)

I use a test kit.... One of these... http://www.aquariumproducts.com.au/prod152.htm

I'll do the complete rang of test tomorrow.... Bugger it, I might even do every single test in the kit. Haven't tried them all yet..

can i still buy your P test?

didn't know there was a test for the P's

JA, isn't bicarb of soda sodium carbonate?????

Funny. When I got into the fish I bought a whole heap if test kits to monitor every thing. but realised it appears I wasted a heap on money. All I really needed to monitor was Oxygen (the lack of is the fastest killer of fish), pH, ammonia, nitrate and for very special occasions copper. The copper test kit is for when I need to add copper sulphate to control blue/green alge but is very deadly to fish if the pH and alkalinity are right. Definitely not for the novice. I would imagine copper is not something you would want to grow plant in either.

Sodium Carbonate Na2CO3 and Sodium BiCarbonite NaHCO3 are different Your should only use Sodium BiCarbonate for alkalinity control. Read this artical
http://fins.actwin.com/live-foods/month ... 00016.html
Plenty of other info on the difference on the net
I buy 25kg bags from a bulk chemical distributer for around $40/bag I think. Dont want to start MYOB to find out I hate that program.

Sorry all my original post I did say Sodium Carbinate I should have typed SODUM BICARBONATE