Backyard Aquaponics
A place to discuss aquaponics

While the fish make a recovery I've been looking at my plants.
I previously had an iron deficiency which the plants have recovered from except the strawberries which continue to have light leaves with a dark vein & a separate issue of black spots / die-back (see photos). I have also used seasol without improvement. And this has been a problem for long before adding salt.
pH has been between 6.5-7.0 for the period.
Are they deficient in something else?
As I post I have buried 1 banana skin in case it's potassium, how many banana skins should I bury?

Get yourself some EcoFungicide (Bunnings)... Potassium BiCarbonate.... and use it the next time your pH requires buffering...

Thanks.
I've seen discussion about use of KOH, which seems quite a tricky and even dangerous substance to utilise.
Is there any reason to use KOH over KHCO3?

That could be a tricky question. KOH and CAOH are both fast to raise pH but they don't contribute much if any carbonates or bicarbonates to the system while using the carbonates or bicarbonates can cause a loss of control of your pH level.

Here is a Video where Nate explains it a bit more http://youtu.be/zP1rUMyklyc

On another note there is Friendly aquaponics that says to simply use coral sand and that there is no need to add potassium to a system.

Keep in mind that each system's source water is different and what needs to be added and how often it needs to be added will vary and if you are fine with a system pH over 7 then the use of the potassium and calcium carbonates or bicarbonates might be appropriate for you in a backyard system. If you are doing "Organic" you might not be allowed to use hydroxides.

Also you want or need a tiny bit of the carbonates in aquaponics for the bio-filtration and pH stability. Most people get plenty of carbonates from their tap water so don't need to add much of that unless they can use a lot of rain water.

I've actually been needing to add a fair bit of hydrated lime because I need the calcium and some magnesium but I don't want to elevate my carbonate hardness too much. I've been using potassium bicarbonate to add a little bit of carbonate hardness as well as increase my potassium levels.

Nate seems to want to avoid carbonates as he suggests it puts his pH out of his control. How are the carbonates useful for pH stability and bio-filtration?

I'm writing my shopping list

I agree with Nate on most things... but not the suggestion that "carbonates or bicarbonates can cause a loss of control of your pH level"

I haven't got sound working at the moment... but I remember watching that video when it first appeared... and something jumped out at me....

To kinda clarify, most of Nates videos really are geared to the people wanting to go commercial. AND he is in a region where the well water/tap water are incredibly hard and there really is little/no rain water so to be able to have ANY control over pH As in to have a pH lower than 8, in a region like that you have to work very hard to minimize the carbonates getting into your system.

I have experience in a location where the well water is that hard but I can, at least part of the year, collect and use rain water. During the dry season when I have to use the well water (which also happens to be our cool season so the fish are not eating as much and the bio-filter isn't being pushed hard) the system pH will be stuck up around 7.6 if I run out of rain water for too long.

However, during the wet season, summer when I could be changing the water with rain water if I wanted and the weather is warm and the fish eating big time, I've found that I can get a pH down in the mid 6 area and I actually need to add some carbonates, bi-carbonates as well as using the hydrated lime and lye because I seem to need a lot more calcium and potassium as well as some buffering and the rain water doesn't supply any of it.

For a backyard system, I would probably just be using the shell grit and potassium bicarbonate but I'm running a more commercial scale system now and I can see how limiting the amounts of carbonates in the system can allow a lower system pH and make it easier to make the plants happy.

Thanks Rupe & TLC

That puts it in perspective! For now (in the mountains) the bicarbonate will do the trick but when I return to central oz and using a mix rain water of harder ground water I will know my options.

Sure... that's understood.... but the video was more related to manipulating pH upward... within a desired range...

Not addressing the question of high pH source water....

(I'll have to review the video once I've got my sound sorted out)


Once your pH is down within this range... your carbonate buffer in the system is effectively nil, or minor anyway...

Any addition of carbonates... by way of system buffering.... will result in minimal, and very temporary elevation of any carbonate buffer....

Adding carbonates doesn't "cause a loss of control of your pH level".... it actually gives you a degree of control....

In the original high pH source water scenario.... it's just a starting point reality... not so much a "loss of control".... and it can be addressed....

I just don't see carbonates... as being quite the "devil" being portrayed... yep in some scenarios they might be a PITA....

I've got my ecofungicide & hydrated lime on the ready!

It really depends on your situation I guess. If by topping up your system that is constantly bringing your system pH up to a pH of 8. Or as I've seen with some people who have misunderstood and go adding lime or shells in the mistaken impression that it will bring their pH down but of course once you go putting lots of carbonates into a system it takes lots of time for them to get used up.

Now as we know having some buffer to keep the pH from dropping too quickly is a good thing but when you get people who want to BRING their pH down to that mid 6 range and their system is full of carbonates and they start adding acid and the pH immediately comes down but then 12 hours later has bounced back up so they do it again and again and again till they over do it ........... Well, it just isn't pretty which is why we usually recommend they adjust the top up water with acid instead of system water......... But again, if it takes large amounts of acid all the time to adjust the system top up water, I just don't personally see that as a good way to go for ALL THE TIME if your well water is that HARD.

As I've been learning this past year, source water can be very different (even moving 17 miles the well water at the old house was quite different than the well water at the new house though they are both quite hard) and chemistry was never my strong suit.

I don't necessarily agree about NOT using carbonates as a flat out statement. But I don't necessarily agree with anyone who makes "absolute" statements about aquaponics since so far it seems almost everyone making those statements is making them through the filter of their own experience about their own source water. Like Friendly say "NEVER use salt" or that you shouldn't add potassium, but of course their experience is with source water on a pacific island and using coral sand as their buffer (which probably adds both salt and potassium to their systems so adding more might be overkill.)

Anyway, we have probably Hijacked this tread enough.....

My 2 sick trout have carked it!
Both with sores - the larger fish has two large sores on the abdomen on both flanks. The smaller fish has sores around the tail.
Is this likely to be from bacteria in the water and possible netting injury? Or worse that there is some other contaminant in the tank?

probably bacterial which is often opportunistic when other stress or injury happens.

How are the rest of the trout looking?.... are they feeding??

I'd say you introduced disease from your Jade tank..... have you had any other Jade Perch deaths???

Now that you've salted both... if the rest of the fish look OK and are feeding then you'll probably be ok...

(although you're still overstocked with the Jades.... and way too cold for them where you are... )

Trout are looking happier, a couple are swimming in the high aeration areas but the others are chasing each other around the tank. They ate a little this morning.


No more perch deaths that I have noticed (my tanks very dark with all the insulation) and they are feeding aggressively on the surface


I know! Plan is to get a system set up for my brother-in-law and transfer some when the weather starts to warm and his system has cycled.
Also, to build some more grow beds. Unfortunately, I missed some cheaper IBCs now all I can find are $100 each.
Anyone in the Sydney / Wollongong know of a good IBC source?