Backyard Aquaponics
A place to discuss aquaponics

"The only catch is the fish" Lol

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Without drilling holes or using a water bridge siphon you could put a pump in there with a float switch so if the water level gets too high it pumps it out. (Recommend putting the pump on something to keep it off the bottom of the tank in case of malfunctions.)

That is a viable option, LowCarbTNPer, and one that I hadn't thought of. Thanks.
I bought a cheap pump with a float switch just last week with another use in mind but haven't done anything with it just yet. I could hang it over the edge of the tank, secured with a rope at just the right depth with its float switch 'arm' adjusted short so that it doesn't pump out 20,000 litres or more once activated. I will do some test runs when I return from interstate and hope that there is no overflow event in the meantime!

Hows everything coming along PJL?

Why will/do you use charcoal?

PLJ you may be interested in my raft concept:

viewtopic.php?f=18&t=13019

I am going to use gangs of these rafts across the top of a half meg freshwater soak already stocked with silver perch (plus FW shrimp, marron, pygmy perch and white cloud minnows), although only low numbers at this stage.

The rafts will hopefully cover completely in cress and be free floating over the soak surface. I am also going to trial other palatable plants such as water parsely and water cress.

I am going to post more pics on the original thread as the rafts grow out. Good luck with your system.

Charlie, I have been over east attending to Defence matters for a couple of weeks but am pleased to report that my rainbows have survived my absence. A neighbour has been dropping in to feed them and to check on water levels in my filter drums, etc and all is good. I can't say the same for one of my dogs though, a beautiful NZ Huntaway, who must have decided to take on a big 'roo and got himself sliced open from mouth to chest. He survived, unlike my bank account after paying the vet!

natmaka, my understanding is that (activated) charcoal, with its enormous surface area through its pores, has a great capacity to adsorb minute pollutants/impurities from the water as they pass close to the carbon surface. It removes chlorine, odorous/coloured substances and various organic chemicals but will let nitrates and sodium pass through. I doubt there is any chlorine in my water but it is stained brown with tannins. I won't mind if my fish water is a little more transparent since presently I only see my fish when they jump clear of the water at feeding time, which is pretty impressive in itself.

Santalum, your raft system is impressive. You have given me an idea for the possible re-use of some bread crates that I have. My understanding is that DWC water needs to have been filtered by one means or another or else a plant's roots will become clogged with matter that will inhibit its growth, and possibly kill it in the way that waterlogging kills a soil grown plant. I currently have about 40sqm of azolla floating in my tank, using up the nitrates and also (I think) contributing to the ammonia->nitrite and nitrite->nitrate conversions via the large surface area offered by its underside, roots, etc. Do cress and azolla survive unfiltered water because they are waterplants, and one could expect lettuces and tomatoes to fail in a similar situation?

Thanks for your comments, feedback and questions.

PLJ I am learning myself and am by no means an expert but am applying my cropping brain to aquaponics/aquaculture. I think it you have hit the nail on the head. I would have thought it depends on the species of plant you go for. Don't think there would be any issues with the water loving plants like English Watercress, Lebanese Cress and Water Parsley. All good live feed for silvers (I seem to remember reading you have a few in the mix) and two legged landlubbers.

No doubt you are well aware Azolla forms a relationship with nitrogen fixing bacteria so you may actually be contributing to your ammonia loadings if the Azolla isn't consuming all the nitrogen itself. Might need a few more silvers in the mix to keep the Azolla in check? In any case a few floating rafts of water loving plants should reduce the surface area available for the Azolla.

You could zip into the local rural traders at Bindi and see if they have any of these crates. I get mine from Bolgart (just down the road really) for free. They usually throw them at the tip because there is no deposit on them. I have been hoovering them up as I have a big water hole to get cover over. Good luck. I'll be posting pictures as the rafts green up.

Hi,



That's true, albeit the effect varies greatly with the type of activated charcoal used. Some are in fact weak when it comes to adsorb ammonia and nitrites (they are better on nitrates). Moreover don't forget to replace it periodically, as indicated by the vendor.



It will remove them, but it will also adsorb some useful things (mainly mineral nutrients) so you may prefer using it from time to time.

Activated charcoal will NOT remove ammonia, nitrites or nitrates... other than any effect it might have as a biological medium for nitrifying bacteria...

The belief that charcoal removes ammonia... is a complete myth... an old aquaria wives-tale...

Hey PLJ just out of interest. Do the Silver Perch definately eat Azolla? I am thinking of introducing it to my freshwater soak but only if I know the Silvers will keep it in check.
Also, like you zapping light idea. Can you make some comments on your experience with that? We get loads of bugs in summer around any lights on the farm and am thinking of hitching a solar light setup at the soak. Thanks in advance.

Santalum, I haven't seen my Silver Perch (Bidyanus bidyanus) since I released them into each of three ponds/tanks back in April so I can't personally verify whether or not they consume Azolla pinnata. I suspect that they do, just as goldfish, koi and other more omnivorous species than Rainbow Trout (Oncorhynchus mykiss) do. In fact, in some parts of the world an Azolla slurry is used as a supplement to regular fish food, apparently with excellent results.
At the rate that Azolla reproduces and spreads across a body of suitable water, I doubt that Silver Perch eating it would make much difference to its overall abundance, unless you started out with just a tiny quantity. This amazing floating fern has many other benefits so should be considered in its own right, I reckon. Actually, yesterday I produced a detailed response to your question re Azolla, including quotes from scholarly articles, etc concerning its benefits and various uses, and then saved it as a draft to finish off later because I hadn't yet answered your second question re bug zappers. Well, when later came the said draft was nowhere to be found , so the lesson that I have learned is to prepare responses in a text editor and then copy/paste into the forum when finally ready to hit the submit button.
I will detail my adventures with a bug zapper next post.

Thats cause your trout ate them all PJ!!! heheh, just stirrin!

Charlie, the trout may well have eaten the 33 Silver Perch that I released into their big tank but 17 of the little buggers were set free in two 128sqm rectangular, concrete ponds. They are taking their chances with yabbies, occasional wild ducks and a total absence of artificial aeration and filtration. As it turns out, they are much more likely to survive than are their siblings that were released into filtered, recirculated water with Rainbow Trout fingerlings. Only in time will the status of these fish be revealed.
Re the bug zapper, I installed a small, residential size unit back in late April. It certainly attracted plenty of moths, some of which were zapped but many just accidentally flew or fell into the tank water and were snapped up by the trout. The zapper function operated well for only a few nights before there was such a build up of toasted insects caught against the electrified wire mesh that I needed to dissemble the unit and clear them out.
The zapper worked well again for a couple of days and then, again, seemed to stop actually zapping the bugs. The black UV light worked well at attracting the moths, and enough of them ended up in the water to make it worthwhile continuing its use. I found myself heading over to the tank a few times a night to watch the moth show, and often participated by catching stray moths against an adjacent shed wall and throwing them in to the fish just to hear the splash of them being taken by marauding trout.
Early on I purchased a timer so that I didn't need to personally turn the bug zapper on and off, since the trout tank is 150m or more from my house. I had also decided to only run it from dusk until about 1am. The reason for this was that I want my fish to be hungry when I feed them in the morning: if they are not feeding then I don't want to be wondering if it is because they have gorged themselves on insects overnight or if they are off their tucker for some more insidious reason.
The black UV light failed about the time of the big blow a month or so back, possibly from swinging back and forth violently. When I inquired with the manufacturer re the purchase of a replacement, I was advised that a tube would be sent to me free of charge due to its 3 month warranty.

Costs:
Electra Zapper $59 (have seen it since for $39 , or $10 second hand)
Electricity - approx 8c per night
Replacement tubes - in the order of $22-$28

A challenge that I face is trying to keep an area of tank surface beneath the zapper clear of Azolla so that the toasted bugs and free falling moths actually land on the water because they are pretty much wasted, otherwise.
Depending on the design of the particular unit it may be useful to cut out the bottom of it to allow free passage of crispy insects to the water.

Got any new pics PJ?

Maybe of some fishies?