Backyard Aquaponics
A place to discuss aquaponics

I agree with you on this GD.. I would love a wide, slightly shallower pond... but IBC's are what I have so I will have to dig them into the ground - anybody want to help move just over 1 and a half cubic meters of stoney soil?

thanks mate - yep, got Malcolm Paul's web site and have been checking out all their plastic ware, thinking of maybe burying or half burying it when the time comes

I think we all know what that is like.

burying will help insulate against both cold and heat... so it can be seen as a positive thing!

In response to my earlier nitrite reading of 5, I replaced about 200 litres of tank water with rainwater. It's lowered the nitrite reading to 2+ (still high) and it's also dropped the pH from 7.8 to 7.4.

GD, I know about "clean" cycles too MY lounge room goes through this! The worst it ever been is when there was a distict "trail path" from the front door to the corridor

Any way, Nice setup!

I'd though (still am) about using those bins, the food factory my unle works at uses them extensivly!

Regarding your nitrites, could be "transplant shock" (just guessing here really!) But it was good to see you test your supply water.

You need to be aware that PH ONLY compe into play with ammonia toxicity, Nitrite toxicity is the same regarless of PH, and 5 getting up there! Shit my test maxes out at this value!

The only this that will lower nitrite toxicity is the presence of Cl- ions (chloride) as in salt.

Definatly keep an eye on it

Are those bins UV stabilised - I know this is not an issue for you GD as you have it in the shed, but am interested for those who may put outside in greenhouse.

The mega bin is mega cool. I need to get on sourcing one - we are surrounded by fruit processing factories here.

VB,

My guess is that they would be UV-stabilised simply because they spend a lot of time outside in hot sun and I'm told that they have a lifespan of about 10 years in regular use.

Sorry 'bout the delay in responding to your question but I've been at a conference on Fraser Island for the past week.

Lucky you. No problems re: the dalay. Had forgotten I even asked.

Can I ask some silly questions? Why do you have a duckweed tank AND a bio-filter AND a growbed (or is the duckweed your grow bed and your primary aim to grow fish and not a plant crop as well?) ? Isn't the point of it to send all the waste water the way of the grow bed allowing the plants to extract all they need? The bio-filter will be a nitrate factory but so will the media in your grow beds (unless the biofilter is temporary until the beds are established *shrugs*). It seems a bit like doubling up to me and the bio-filter will only be a nitrate factory if it stays aerobic all the way through. A risk with tall drum like bio-filters is that they actually become nitrate digestors towards the bottom because the oxygen becomes depleted as it passes through so that by the time it reaches the bottom there isn't enough to support aerobic bacteria and anaerobic bacteria begin to grow that metabolise nitrate instead of oxygen. I am not sure why you are using oyster shells as your media either. A small amount is good to buffer the water to maintain a pH of about 7 but too much will increase your pH (and therefore convert bound ammonium back into ammonia) and will increase your hardness as well which may result in calcium deposits in your system. I have probably misunderstood you somewhere along the way...

Hi OzV,

We're experimenting with duckweed to confirm the optimum conditions for intensive growth of the plants in a small space. We will have grow beds once our system begins to cycle properly. In fact, we'll introduce our first plants next weekend.

Bio-filters are used to assist the conversion of nitrites to nitrates pending the installation of growing systems. Our biofilters are aerobic all the way through - the water that drains through them draws air down with it. If you look at the photo elsewhere in this thread, you'll see that our bio-filters are squat drums.....but it doesn't matter since you'd need very long cylinders (and lots of water) before oxygen depletion became an issue.

If I decided to use deep water culture or NFT, I'd certainly use bio-filters. As it happens, we'll use a mix of growing systems and bio-filters are useful for developing bacteria populations. Gravel grow beds are just flood and drain bio-filters.

We use oyster shells because they help to keep our system's pH at acceptable levels, given that we use rainwater (which is acid) for water changes......and oyster shells are frequently used in the bio-filters of commercial fish farms.

Ahhh - an experiment - that's what you get for coming in at the end of a conversation

It's funny you know - there are a lot of contradictions between aquarium keeping and aquaculture/AP (a huge number of parallels too). For instance a method I use to filter water in my 630litre marine tank is a deep sand bed where only the top inch is aerobic and the bottom 4 inches is anaerobic. It takes very little distance to create anoxic conditions in this system. Another contradiction is combining several different filtration methods. It has been shown that running a deep sand bed with another filter source, like a large canister filter or refugiums, will actually impede the effectiveness of the deep sand bed and the associated infauna in aquarium systems. In aquariums (even large ones) we often use small amounts of crushed coral, shell grit, or oyster shells to buffer the water and maintain a pH of about 7 but we wouldn't use it as the filter media itself (unless we had marine tanks or maybe rift lake cichlids). When you say do you mean that you will use the bio-barrels to help establish new systems by relocating them from mature systems to the new systems to help establish a grow bed? That is something I do in aquariums too. I always keep spare filter media going in tanks so if I need to set up a new system I can transfer it an so pretty much avoid a cycle.

I saw those red barrels you are using as the biofilters - they looked pretty tall to me *shrugs* it would be interesting to do a D.O. test on the water going in and the water coming out to see just what is consumed...

Thanks for taking the time to explain this for me.

OZV, don't forget that in marine aquariums the deeps sand bed it really cool, becasue of the problems of removing nitrate. The reason that there is only a very small depth difference between aerobic and anoxic id becasue of the minimal (almost none) flow of water thoguh the DSB.

Steve

OzV.....don't take the duckweed experiment too literally at this stage - it's not doing what we want (probably due to daylength and light intensity issues) and so it's probably not impacting our system too much.

The trickling bio-filters that we're using are never without air because, unlike the sand filters that you've described, they are filled with media which feature lots of air gaps through which the water from the fish tank trickles. In fact, the water coming out of our bio-filters would have a higher oxygen level than the water entering them.

The other reason for using bio-filters is that we can periodically use some of the media in the bio-filter (currently oyster shells and clay aggregate) to seed other growing systems. For example, this weekend I hope to set up five satellite pots filled with clay aggregate from the bio-filters. They will each become small grow beds. We'll then replace the clay aggregate in the bio-filters with more oyster shells.