New system, should I lower PH

Cylo

dlf_perth wrote:

oxygen & salt ath the moment as Mr damage says...

wait until they sit firmly at 0-0.25 (ie. no purple shades, ideally light blue if you use API test kit)
before reducing salt levels.

prolonged elevated nitrites can have a negative long term effect on fish
(ie. physical damage)

Cheers, thanks! Will do now

With hindsight I'm the kind of person who would prefer a fishless cycle but I didnt read enough online & wasnt aware it was an option

I asked for advice from the aquaponics shops in sydney and newcastle when to put in fish while enquiring re purchasing fingerlings, they simply said to put fish in at the same time as the plants as they both dont work without the other. They didnt mention anything about fishless cycling, seems they are doign fish an injustice not informing novice ppl of basic information they should be aware of.

Cylo

Just thought id update

Theres no nitrites or ammonia showing up on API test kit, approx 5ppm nitrates

Im assuming its cycled, nitrites got to 1ppm maximum for 3days and now nothing. Will check again tomorrow

I stopped feeding once the nitrites showed, ill give them some now.

Mr Damage

Sounds like it.

Cylo

new system has been running well for the last 8days, no ammonia or nitrites and approx 20ppm nitrates. all fish still going well

thanks for the help!

Mr Damage

Cylo

Id like to incorporate a DWC grow bed into the system to get some experience with it.

From what I've read so far I would need to add a filter or 2 to supply clean water & prevent clogging the roots in dwc, Ill need to determine what size dwc bed will be and then whether I will have enough fish to support & possibly need a sump, lots to learn

Do you guys know without searching of a thread or 2 where others have done the same.

Thanks very much!

Mr Damage

If your Wet gravel:Fish ratio was well balanced before adding a DWC component to a system, then there's a good chance you'll run into nutrient deficiency issues once you add the DWC bed.

A few years ago, with the help of a couple of customers that were willing to experiment, we determined that if you increased your GB depth from the standard 300mm gravel depth (250-260mm wet) to 400mm (350-360mm wet) and increased your fish numbers accordingly (ie: 4x Trout or Barra, or 5x Silver Perch per m2), then it can support up to the equivalent sqm of DWC if running small leafy greens, ie: Lettuce, Asian greens, herbs etc.

For example... If you had a system with a 1sqm GB with a 300mm (250-260mm wet) gravel depth and you increased the gravel depth to 400mm (350-360mm wet), stocked with fish accordingly, then you could add another 1sqm of DWC bed growing small leafy greens.

If you don't have a sump tank now, you won't need one if you add DWC bed.

Cylo

That sounds interesting, thanks very much. Will continue to give it some thought

At the moment the ph hasnt dropped below 7.5, would it be ok to do say 10% water changes each day or 2 using rain water to try getting the ph down to 6.8 or 7? Seems maybe the carbonates are still too high, as youve explained previously they wont allow the ph to drop as it should do when cycled. Is rain water low in carbonates or does that vary, if it was low then using it should drop ph slowly each dose and also be lowering the carbonates in system. I realise we dont want to remove all carbinates either as they will help buffer from a large drop

If rain water is not the better option then I assume I should use a seperate storage of tap water and add acid over a few days as you previously described, until the carbonates are removed enough to maintain a ph a few points lower than in FT then continue this until getting to 7

The plants are yellowish which is why I'm interested in speeding up the lowering of ph rather than leaving it to lower in its own time.

Mr Damage

Cylo wrote:

they wont allow the ph to drop as it should do when cycled.

The natural pH decline won't necessarily happen as soon as the system is cycled, it depends on the level of carbonates in the water and the amount of nitrification taking place in the system. If your pH is 8.0 or lower I would leave it and allow it to di it's thing naturally. You can still achieve good plant growth at a pH of 8.0, I had a system sit at around 8.0-8.2 for a couple of years and still had excellent plant growth.

During summer, when there is a lot of evaporation and transpiration taking place, the top-ups should be done with HCl acid treated top-up water or rain water, otherwise the carbonate level can actually increase.

What do you mean by "yellowish"?... Have any pics?

Cylo

The PH is back to 8, doesnt that prevent the plants from absorbing certain nutrients?
I may have planted a few too many plants before the fingerlings have grown, as the nitrates are not showing up now.
Is it acceptable to add a capful of powerfeed seasol to substitute for lack of fish until they have matured further?

Mr Damage

Iron and to a lesser degree, zinc, may start to be come less available at that pH or higher, but I had a system run for a couple of years at a pH of 8.0+ and still achieved healthy plant growth.

Treat any top-up water with HCL acid as previously described, so you aren't constantly adding to the carbonate level, and are assisting the acceleration of the natural pH decline. Then add a capful of standard Seasol per 500L, per week (2x capfuls per 500L with Tomato plants in there)... and let nature do it's thing, it takes time for a system to build up a nutrient bank, and Tomato plants in a new system don't help with that.

Don't use Seasol Powerfeed, it contains a fair amount of Ammonia and with a pH that high and the water now warming up, even the slightest whiff of Ammonia will kill your fish. At a pH of 8.0 and water temp of 28C an Ammonia level of just 0.2 (whish is lower than the first reading on an API Ammonia test kit) will be starting to harm your fish.

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