Backyard Aquaponics
A place to discuss aquaponics

Aha!

I can see an excellent opportunity for an afternoon experiment over a cup of coffee

I shall endeavour to optimise the cycle.

I agree... I used to have my tommies system constantly flooded every hour until I found out that I didn't have to do that.. so I had it retimed to flood every 2 hours and they grew like mad. grew to 1 and half metres tall in 2 months even with only 3 hours of morning sunlight.

so yeh, the plants like to take a breather.

Tomato's , The problem i see here is the small seedlings need the water level hi enough in the bed to get their water ,, but as the root system grows tomato's are very liable to get fungal deseases etc ,root stem rot/desease can be reduced by dropping the water hieght. Those with the looped hose type drain should find that a quick and simple adjustment.
Also make sure there is no splashing water around tomato's ,, this is one of the main ways that fungal deseases are spread to leaved etc

so how much no water time is good for tomatoes?

I've grown all mine with the normal 15/45 on/off timer style systems... although in the heat of summer I have adjusted the timer to 15/30....

My system has the pump running all the time and the flood and drain happens by loop siphon. I can say that cherry and grape tomatoes grow like monsters (I tend to always grow indeterminate varieties so they just keep growing and growing........) anyway, my beds fill and then they drain and start filling again, probably happens 2-4 times an hour.
It is important to have a good level of gravel above the water line so the surface stays dry. Also probably a good idea to try different varieties of tomato to see what fares well in your climate. Some will do better in hot/humid conditions than other will.

Okay, the growbeds drain almost completely (probably 90% or better) within 15 minutes, and they take 5-10 min to fill up. So, I've set the timer on mostly 15-on-15-off with a few 30-on-30-off for good measure (just to make sure that at least a few times a day the growbeds will definitely fill up 100% and definitely empty 100%.

My nutrient loads are still a bit iffy. Ammonia is being nicely dealt with (0 ppm), and nitrates are relatively high (20 ppm), but nitrites don't seem to be going down at all. I find the colours very hard to delineate between 1 and 5 ppm, but if I had to guess I'd say it's currently sitting at around 5 ppm nitrite - the maximum level on the test kit.



Is it normal to have an extended period of high nitrite, and is this level dangerous? I wonder if the bacteria reach an equilibrium, and since the plants aren't yet stripping out all the nitrate perhaps the bacteria aren't producing any more nitrite. Alternatively it could be that the nitrite-eating bacteria are growing very slowly due to the cool temperatures.

Temps (measured in the morning) are consistently around 11-11.5 deg C, and pH is sitting at around 7.4

The fish are feeding vigorously so I presume they're pretty happy.

I would say the cold weather is hampering the effectiveness of your bacteria with the increased fish load. I would chuck 3 ppt salt in there if you haven't already to help combat the nitrite levels, and look at doing a bit of a water change. Easy on the feed too.

Nitrate levels at 20 are still low so no worries there.

Okay, it's been a few days between readings (darned early starts!) but today I've had encouraging results:

NH3: 0.25 ppm
NO2: 0.5 ppm
NO3: 40ppm

Temp: 12.4 deg C @ 5pm
pH: 7.4

So... The Nitrite spike has really subsided (was around 5 ppm a week ago) so I think I can get away without salting or doing a water change.

Fish are still happy, eating very vigorously. It's so much fun to feed them when they splash around like this!

Seeds have sprouted in the growbeds so they will soon be contributing to the nitrate-sucking effort.

The plants look a little deficient (brassicas and coriander are a bit yellow; basil has brown spots); I've added a couple of teaspoons of Iron chelate and will continue to do so once a week from now on.

Should I add more Iron than this?

Should I add any Seasol?

chuck it in. if you think it might help, it probably will

basil season is over jimmy unless you have a hot house, you might as well pull it out.

Oh well, that's a relief!!! I thought there was something terribly wrong with my system!

nope, just the season

Bollocks...

move to the adelaide hills rupe then you will see how the other half live