Backyard Aquaponics
A place to discuss aquaponics

Les and AA,

I think I prefer the dangle in a bag method......for greater exposure to moving water.

Because my system is only 600+ litres, I have to top up regularly so I'm thinking of putting water into a drum, adding a pre-determined amount of a buffering agent and then pumping it into the tank. That way my water is always at the right pH.

I find that, with the tendency of these systems to become slightly acidic and the naturally acidic rainwater, the shellgrit idea is alway behind the game. I also have oyster shell in my bio-filters but they don't contribute much in the way of alkaline balance.

I find that I always have some ammonia, nitrite and modest nitrate levels in the water.......and I'm wondering if the reason is that the system, at pH 6.6 - 6. is always just below the optimum for cycling.

I think Steve summed it up when he described it as "slowing down" rather than stopped.

The lower (than others) nitrate levels may be the consequence of lots of air in the tank. As you are probably aware, nitrate will flash off as a harmless gas in the presence of plenty of water movement.

The other possibility (and the one that I think is more likely) is that the existence of ammonia and nitrites may inhibit the growth of the nitrobacter needed for higher nitrate production.

What's your view......Steve or AA?

Gary

The nitrite itself should promote nitrobacter as there is a constant food source. I wasn't aware of nitrate flashing off, no. Very interesting. My 600 litre pond is 0 nitrate system at present with a pH of 6.6 - 6.8. Lot of aeration and water moving.

My wee system (approx 200 litres total) is around 80 ppm nitrate and pH 6.1. I'm adding shell and changing water there now to try bring it up a bit for safety's sake. It's sat at that pH (6.1-6.2 ish) a long time now. Never bothered me, and slow -certainly wasn't.

Though if the optimum is higher it's possible I can go beyond explosive growth and get nuclear on it.

I asked about shell as you use rain water. I want to use rain water but thinking about the fact I'm in a city full of "spray whatever the salesman tells you to" type gardeners, I'm not sure it would be wise. Maybe I'll just collect it for the dirt gardens as I hate watering in chlorine. The dirt gardens obviously get the same dust etc that is on the greenhouse roof.

The gas that flashes off - nitrous oxide? If so, no wonder I love my greenhouse

I'm thinking the ammonia and nitrite will be at least partially attributable to the lower pH as you are stocked fairly heavily for 600 litres. With higher stocking water parameters can be hard to meet, hence the scientists pulling out solids etc to keep the water quality.

You're still doing a fantastic job, love to hear Steves slant on things too.

Hi Doug,



The temperature here, at the moment, is 34 degees Celsius (93 degrees Farenheit) and the humidity is high....and we're sweating our backsides off. The temperature inside my fish tank is 24 degrees C (75 degrees F) and the fish are as happy as pigs in poop.

The weather in south East Queensland is like this for about 3 or 4 months of the year. The rest of the time it's cooler and less humid.....beautiful.

Gary

AA,

While I have low nitrate levels, it doesn't seem to be hindering growth too much.......as you can see from the photos.....I just don't seem to get the high nitrate readings that other folks experience.


Gary

Yep Gary - I am leaning towards putting shellgrit in shadecloth and dangling in the water flow path, I did a test a month ago with SG in a bucket of rain water - took ~1 day to rise from 6 to 6.8 PH without any agitation.

My small system got down to low 6's and hence the tests, the new big one is ~7.4

Les,

I experienced a similar jump in pH when I got all the dust out of the bag of shellgrit and ran it through my bio-filters. Now that the dust is gone, it's a much slower process.

As I said earlier, I'm thinking of using something that I can just dose my top up water barrel before I pump it into the tank. I've also got to get my head around water hardness chemistry so that I use the appropriate stuff. Once I know what I need to do, I can avoid any peaks and troughs in the fish water.

By the way, I'm following your latest experiments with interest. What was your calling prior to AP?

Gary

I have hust put my grit into a hydro basket buried in the grow-bed. THat way it gets the flood and drain action. The grit is wrapped in a gauze of sorts.

......and another good idea. Thanks VB.

Started out as an electronics technician in the army - better not say which year but it was way before some forumers were born

vb - that would work very well me thinks

Visited there more than once when at Vic Bks (Bris), our unit was in charge of all the communications for the services in Qld - so did a few swans (Cairns,Tvl, Darwin)

moved it to your system Les so Gary didn't get hijacked

Was that when the army had steam driven generators

G'day Gary,

Thanks for the get together the other weekend. Impressed with the coco peat beds. Any advance on you / Murray coming up with a lower cost bulk supply? I am expanding my system and would like to try coco peat, about a 500 litre bed.

Rod

RR , supplies By the end of this week

Muzza

Hi,

I've been wanting to trial the production of fly larvae for use as fish food for some time.

I wanted to achieve this without getting into the putrid mess that some fly species seem to prefer.....so I decided to try something fairly innocuous like bread soaked in milk.

I've had to wait for three days for the bread and milk to become sufficiently "interesting".....but it's starting to happen.

Interestingly, this stuff smells like stale beer......a yeasty sort of smell.

Here's the first photo.

Top idea GD, will you wait until the maggots get fatter before feeding them to the fish or put them in at this stage