Backyard Aquaponics
A place to discuss aquaponics

Have never tried growing in them so thought I would give at least 1 a go.. Would like to grow the majority of our greens in the system & it looks to be the best method to do that from what I have seen..
Still a few kinks to iron out like how I'm going to add extra O2 into the bed.. If I don't like them I can always just tip the media back in & away we go

I guess it just seems like a lot of extra work to take the media out of existing beds.
If the conditions for the two beds are very similar (lighting wise) I might suggest you leave one as media and make the other Raft and try to plant the same things at the same time in each and compare results.
Raft beds can work well but they do require some extra stuff like starting the seedlings usually in some other media that is often not as re-usable, most people also use net pots which add to the costs since those don't always survive long term re-use, having rafts, separate filtration, and the additional aeration.
Most commercial operations use them because dealing with such huge amounts of gravel or media would be extreme AND the extra maintenance and transplanting is par for the course in commercial planting. It also lets them use automatic seeding machines to plant trays of seedlings and keep the trays in climate controlled germination chambers then move them out to a seedling area that is more closely spaced than the grow out raft so it is a bit easier to save on space though the moving/transplanting requires more labor.
You have to decide which of these things matters and what doesn't in a "home growing" situation. Do you prefer to do your planting in trays sitting indoors by the TV and then keep the tray under a dome indoors for a couple days before moving out to a seedling area for 2-3 weeks and then transplanting into the rafts? And do you have a good seedling area that will keep the seedling trays appropriately moist while giving them plenty of light to produce nice stocking seedlings? Do you have a place for the trays indoors that will be the right temperature for germinating the seeds you intend to grow?
If you don't have those things, then some of the benefits of raft growing will be minimized. Getting an air pump or small blower and air stones is not difficult, just gotta bite the bullet and buy them and then commit to the extra electricity use to run them.

The beds are very sludgy & I think the reason the pH drops 0.1-0.2 every day.. Would rather not have to add lime to help adjust it regularly.. The beds are not flat based so would of been collecting the solids in the ribs for well over 18monts now, 12 of those without a solids filter on the system at all Was told that worms would look after all the solids by an online guru but I don't think that is the case somehow




We are in the subtropics & start all our seeds outside so need no extra room for seedling propagation here..
Also looking at switching the air compressor back on (been running on venturi for a while now) to aerate the moving bed bio filter as well as the digester/mineralisation drum & will have air to spare for at least one raft bed.. Also looking at using soil filled grow bags (smart pots) in the system as well..
Is all a bit of a learning curve & will be interesting to see how it all goes..
The moving bed bio filter that is going in here will be as large as the one that is being built for the larger RAS.. If the aquaponics do start to go pear shaped I can turn the grow beds off & run the system as a RAS then turn the beds back on when its sorted..

Well, that's the grand plan, yet to see what it looks like in reality
Cheers TC & thanks for the post.. I like looking at this from all angles

Not much really to report here except for the constantly falling pH issues..
Have noticed that while some say that its a good idea to keep the pH down around 6.2-3 I have noticed that the Jade perch feed a lot better when it is sitting 6.5 or above.. Has anyone else noticed what pH their Jades feed better at ?

Hope to do another AP clip once I tidy a few things up.
Cheers all..

In a system with a properly functioning bio-filter and the fish feeding well, the pH is supposed to be dropping and it is really quite proper to be adding buffers to keep the pH up where you want it. The use of these pH elevating supplements is also usually used to make sure the calcium and potassium content of the system are high enough to support plant growth.

I know some people don't have much need to add buffers because their source water provides plenty of lime and other people have problems because their source water has so much lime that the pH never comes down.

Build up of gunk in the grow beds might be providing an extended amount of nutrients for your system but actually the sign that a grow bed has gunked up too much and is causing a pH problem is actually the other way, a rising pH that can't be attributed to high pH top up water, media, or algae is a sign that there is an anaerobic zone in the system. Grow beds giving off a nasty odor are another sign that could mean there is a build up of solids that has gone anaerobic.

Personally the only "clogging" with gunk from fish tank I've ever really experienced in gravel beds was in a very poorly designed set up where a really tiny grow bed was getting all the flow first and it clogged up but the mint planted in that bed probably also contributed to the problem. All other grow bed clogging I've ever experienced was due to overaggressive plant roots (Banana, Lufa, Mint, Bamboo.) If there is enough grow beds for the fish load then I seriously doubt there is enough fish waste solids in a bed that has only been online for 18 months to cause an issue. However, if you are talking about a system that has had way way too many fish for the amount of grow bed, then I suppose it is possible for a bed to get totally slimed up.

I have a system that I use for quarantine and I must admit that it gets totally overloaded (by about 4 times the amount of fish it should get) for the media bed solids handling capacity on a regular basis and the "overflow" bed which gets all the excess flow that the two siphon flood and drain beds can't handle is totally slimed up much of the time. It serves as my example of what NOT to do. I'll be replacing that bed with a radial filter when I get a chance since it is in too shady a location to grow much in the way of plants at the moment anyway and my worm bins would appreciate some nice fish goop more often.

But anyway, if you really want to play with a raft bed, then play away........

Thanks for that TC.. I was told that it could be due to solids building up with the pH falling due to the breaking down of the bacteria.. My big concern is the speed that it drops, 0.8 in the past 2 days (was down to 5.8 yesterday) which I just cant understand.. The water temp here is staying between 23.5-24.5°C/74.3-76.1 °F.. I know no one can diagnose over the net but am grateful of any suggestions

The water here is very hard.. Not uncommon for it to come out of the tap close to 8.8.. Used to try & buffer it before adding to the system & gave up as it just kept bouncing back up in a few hours after acid was added.. It does come in handy to raise the pH though

Have only had 30 Jades with a few goldies for a while.. There is 900L/237gal of clay as the media which according to Paul from Earthan group & info Dr Storey has posted, there is more than enough media in there to handle the load..

Our beds are dodgy (have sunken rails) in the base so that's what prompted the whole redesign of the system.. You can see the gunk sitting in the low spots through the unpainted base of the grow beds :/ Just a newbie mistake that needs to be fixed really
I have IBC with flat sides that will be cut up to replace them but though that the existing beds could be used as raft ones to save cutting up another..

Thanks again for the info TC, really appreciate it.. Want to get it sorted in my mind before we move the system about.. Don't want to make a mistake that cost us the fish..

Hi Rob,

I'm buffering my system up every week at the moment too just to maintain my PH around 6.4.

While the warmer weathers here and the fish are feeding flat out the bacteria are producing a lot of acid.

Both systems are running almost the same only a slight dif. because one has river gravel media beds and the other has local blue metal drainage gravell (with higher carbonate levels).

I'm alternating each week between adding a small amount of either agg lime or Potasium bicarbonate or sodium carbonate. I'm also adding any egg shells we get and a few handfuls of shell grit.

in the winter months this is more like a monthly requirement as my systems slip into a slower metabolic rate. That's my experience any way and it was the same last summer.

Mery Xmass and Happy new year mate,

Doing it most days here at the moment Freddie.. Adding about a Tbsp of the Hydrated lime into about 4L of water & splitting it between the 3 GB's..Find that looks after the nights fall & raises it by about 0.2-0.3 if that make sense..


Where are you getting the potassium bicarbonate from? Have added some eco rose but gets a bit expensive after a few additions

Hope to be up at Bears on New years day to pick up the K1 but more importantly to suss out his systems Still haven't made much of a start on our RAS but hope to before B goes back to work..



Same to you with a santa hat on


All the best to you & yours mate

Hope to be up at Bears on New years day to pick up the K1 but more importantly to suss out his systems Still haven't made much of a start on our RAS but hope to before B goes back to work..

Bear mentioned that, I'll try to drop up and say hello (going to Woodfordia for news year eve, could get a little messy)

You also welcome to drop in here for a quick visit on your way though if you like..

food grade potassium bicarbonate can also be found a brewing/wine making supply shops or online supply places.

If using only hydrated lime to deal with pH you are only getting calcium and while the calcium hydroxide will raise pH it doesn't do much to act as a long term buffer. If you don't want to be dealing with adding it daily. You might get a paint strainer bag or an old stocking and put a hand full of shell grit or limestone chips and hang that in your system where the water flow will go through it. I recommend using the stocking or paint strainer bag because if you get too much calcium carbonate in a system you can wind up with the pH too high and have to wait a long time for the carbonates to be used up before the pH comes back down again. At lest with the bags you can pull it back out if the pH seems to be rising too much or move the bag to another location if it doesn't seem to be effective just hanging in the tank or something. You want to make sure you get the pH close to your desired level before depending on the shell grit bag since calcium carbonate is slow acting it will function better to help keep your pH up rather than bring it back up if it is way low.

In my location, my well water is so hard that if I'm constantly topping up my system with well water, my pH doesn't get much below 7.6. But if I get to go a few months letting rain water fill my system, my pH can drop into the low 6 area and I have to start adding buffers. Just because source water is very high pH doesn't automatically mean it is really hard but just that it is alkali. Some water treatment plants may use calcium carbonate to bring the pH up in the tap water to help protect pipes from corrosion and let the chlorine work better and others might use the hydrated lime which will raise the pH but won't introduce much carbonate which can build up in pipes and cause problems for plumbing fixtures. I'm not sure how you get really high pH well water without having lots of carbonates in the water but I expect there are ways that can happen. I'm personally experienced with the well water in my part of FL where it is out of a limestone aquifer and we are in a region of heavy rainfall (at least part of the year) so the chemistry of the ground water here is such that the aerated well water can have a pH between 8-8.4 but the Hardness is quite high like 180 ppm carbonate hardness one of the times I tested it here at the new farm.

I know Nate recommends avoiding adding much carbonates in the system but by doing that you have no buffering and have to deal with keeping you pH up almost daily. By adding carbonates you do take the risk of adding too much and winding up with them being high and not letting you get the pH back down easily but with the careful use/addition of some carbonates you can perhaps avoid having to deal with raising pH every single day.

Have shell grit all through the clay around the in flow to the beds as well as on the floor of the sump tank TC.. Found that it worked as a buffer for a while then stopped.. A mate pointed out that it works well as a buffer while the smaller particles/dust is there to dissolve but not so well with the larger bits.. Might try whizzing some in an old food processor to see if that helps

That's a high pH your dealing with.. & I though ours was troublesome :/ Haven't done a hardness test on ours here as it changes all the time but probably should..
With the way our pH falls I'm not to concerned with a carbonate build up at the moment but will definitely be keeping an eye on it..

Off too look for potassium bicarbonate again now as the eco fungicide is just to exy to keep adding.. Tried our local home brew but they were shutting down & had sold out..

Cheers again TC & hope you & yours have a great one..
Rob.

Will see how we go Blind Freddie.. We are stopping off at Bears on the way to a New years do so might not have time this trip up..
Thanks for the offer & it would be good to catch up.. Is your RAS up & running yet ?
Cheers Mate & all the best to you & yours..
Rob & the girls..

It is also possible that shells have lost most of their carbonate already. Smaller particles of course will dissolve easier but there are some kinds of shells that can have all the carbonate dissolve and still seem to be basically intact I guess. And some people find that enough bio slime can build up over the surface of a bag of shells that it needs some disturbance every once in a while to keep it functional.

I think most aquaculture operators think that a carbonate hardness level around 50 ppm is mandatory but I think I've seen that guys like Ryan or Nate are probably running something lower like (don't quote me on this since the slide went by o fast I couldn't take notes) 20 ppm.

With the hardness test I have it isn't all that fine or accurate but one drop is too low (basically saying there is not carbonate hardness left and the pH is probably close to 6 or lower) in my opinion 2-3 drops for the change is about right (as in I can have a pH between 6.5-7.2 when the carbonate hardness is only 2-3 drops) and anything higher is going to give me a pH of 7.6 unless I start playing with pH adjustment with my particular source water.
The exact level of carbonate hardness and pH you can maintain with that hardness will depend on what exactly is in your source water, media and what you use for pH adjustment. Some buffers tend to keep the pH even higher than other buffers and I don't think all lime is the same. Apparently at Friendly Aquaponics they can simply dump a whole bag of their agricultural lime into the system and still have a system that tends to maintain a pH of right around 7. Well their lime is basically their beach sand which isn't sand so much as shell grit (again, remember that some kinds of shells buffer pH higher than other kinds of shells and some dissolve quicker and others slower.) Around here when you buy agricultural lime it is most likely pulverized limestone and it is easier to find chicken grit that is just little bits of limestone rather than crushed oyster shells. Many people around here with aquariums that need to keep the pH buffered up, will actually use large chunks of limestone Rocks as decorations in their aquarium that serve the added function of buffering their pH.

There are many things you can do. Just make sure to keep your experiments simple (don't try multiple things at once since you won't know which thing worked) and if you are adding supplements or pH buffers that you can't take back out, use very small quantities so as not to go too far in any one step. Nice thing about the grit in a bag or large rock is you can remove them it they are having too much effect.

Hey Rob just wanted to say I love the pictures you put up on your Facebook page, you've got it going on! I have your videos on my list of things to do...

Hi Rob hows the RFS Coming along? I hope to start on the new RFF for mine this weekend and will then incorporate a Matala style filter after that before it hits the bio filter. Cheers

Any thing new Rob, have my RFS up and running just need new fingerlings. Cheers