Backyard Aquaponics
A place to discuss aquaponics

Hi All. I've lost approx half of my silvers in the last 4 - 6 weeks and think i have exhausted my search on AP forums looking for answers. I'll attempt a summary of events.

About 3 months ago I added 2 new 250 litre grow beds and added river gravel from local gravel company which was rather muddy and after lots of cleaning added to grow beds expecting that things would clear up in time. Never did. Hadn't seen any fish for ages but they were eating fine so I knew they were there. I had an 1000 litre IBC tank for 100 silver perch (Yes, I now know not to stock that high, some bad advice that i took.) We had a mini heat wave and the temps got up to 32 degrees for a couple of days and a few fish stopped fishing. I realised that having a larger tank would be easier to control temps so I installed a 3000 litre tank and as i was transferring the fish over I noticed . Most the fish, had white spots, anywhere thru to total red sores. Fish anywhere from 12cm up to 30cm. They looked alot like this..

Ummm... How do you post photos on here??

I've been keeping regular checks on the levels. The PH is up at 7.4 (has been like that since the new gravel), the Nitrites at 0, nitrates at 20, but ammonia just hovers above 0, but have recently been able to return this down to 0.

After adding fish to new tank, I salted the tank to 5ppt, let it run over night, and then drained half the water out and replaced with tank water the following morning.

The temps in the new tank have been sitting between 25 to 28 degrees, the remaining fish are all swimming around ok, but they are not eating??

See Iif this works. This was the latest casuality. Was only about 12cm. Sadly i see another one about 30cms swiming around with similar sores?? Plz Help....

Also noticed sores near gills.

Yeek... looks like.... Aeromonas salmonicida

http://www.daff.gov.au/animal-plant-hea ... al_strains

Note the part that says...



I'll see if a salt dip/bath can be effective...

Don't know wether to laugh or cry.. My system is about to hit one year old.... Happy birthday... So the remainder of the fish are probably infected.. How do they get this disease??

Aquarium guys would suggest "Melafix"... for mild cases, and usually not enough on it's own...

Or Methylene Blue... as it penetrates the skin tissue, and can treat internal symptoms....

But I'd be hesitant to use either...

In aquaculture... it would probably be oxytetracycline... an antibiotic... but only available under vet perscription... and some fish have developed resistance....

Salt baths will probably help for external signs... but the water body could still carry the pathogen...

Hesitant to suggest it... but "Condies Crystals"... Potassium Permanganate would treat your water, and kill most of the bacteria... and a UV filter might be beneficial to some extent...

If you were to use Potassium Permanganate... it's a highly reactive oxidising agent... which could such the oxygen out of the system.... so aerate like mad...

Primary cause... apart from all the usual parameters... would seem to be a high suspended solids... organic matter...

So putting on an external canister filter, with UV might help as well...

Using a treatment tank/bath would be the preference... in conjunction with salt... but your whole tank migh benefit from treatment...

If preparing your own (dry) Potassium Permanganate treatment, use 2 ppm per liter of water for in tank (pond) treatments and up to 10 ppm per liter for 10 -30 minute baths.

For already prepared Potassium Permanganate (in liquid form), use double the recommended normal tank dosage for a bath.

Care must be exercised when using this product, whatever level dosage is used.

It is a strong oxidizer that when added to water will give a deep purple color that will slowly turn brown/yellow as it oxidizes (the more dissolved organics, the more quickly the change of color to brown/yellow which indicates the oxidation properties are mostly spent).

It can be used as a special-purpose freshwater conditioner for ponds and aquariums, because of its ability to improve water quality by oxidation of excessive dissolved and suspended organics.

The chronic presence of excessive dissolved organics in the water promotes the growth of potential disease-causing bacteria such as Aeromonas, and as well lower KH and pH.

However it should be noted that initial oxidation produces Carbon Dioxide which will initially lower pH/KH and I recommend a water change a day after the use of Potassium Permanganate for the purpose of oxidation of organics in ponds or aquariums.

The action of Potassium Permanganate proceed more rapidly under acidic water conditions and higher temperatures, while the action is less rapid at higher pH and water hardness.

Do not combine with de-chlorinators as these products are reducers (usually container Sodium Thiosulfate or other reducers) that will immediately remove Potassium Permanganate since it is an oxidizer.

Please keep in mind that this is an oxidizer than can and will destroy beneficial bacteria, so use with care if you must treat your main tank (which is why I prefer baths or hospital tanks).

Also note that Potassium Permanganate suppresses photosynthesis in plants in the water, although this can be beneficial, especially in ponds with large amounts of decomposing organics as this will increase oxygen levels in the pond, particularly at night.

In this process Potassium Permanganate reduces biological oxygen demand, and improves water quality and clarity.

Don't feed for several days after treatment... and test your water parameters... especially pH and ammonia....

Thanks Rup... Thats alot to digest, if only the crystal ball would predict the outcomes. if the disease is in the fish, and the water, and then possibly grow beds and then maybe the plants? and after all the treatment bringing these fish back into the system after the salt/crystal baths, there is every chance that I will probably bring the disease back into the the Ap system. If the fish seem better, would it be something that you would want to eat? Would i maybe be better cutting my losses, removing the fish, emptying the system of plants, water and gravel and starting all over?

Concerned at that quote

Quote:

Fish surviving disease outbreaks are recognised as carriers of the disease and may continue to infect the remaining population without themselves showing any outward signs of infection.

I used melafix in my system before, it's easy to get hold of, and based on the extract from the cajaput tree (spelling). Not for use on eating fish though....

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Which is why, although a seperate tank/bath is generally preferable... but as your outbreak is severe... you will probably have to treat your tank...

The plants will be fine.... they don't take up the bacteria.....

The gravel will be fine as well... as the treated water will turnover within an hour (usually)....

And the treatment... along with salt (6ppt).. for two weeks.... should see the bacteria killed off....

As I said, an external canister filter with UV.... will also help kill any water bourne bacteria, without being too determentail to the nitrifying bacteria....

The initial treatment... being basically anti-bacterial... will have a short term "hit" on the good nitrifying bacteria...

Hence the recommendation to stop feeding... and test... for several days afterward...

The Potassium Permanganate breaks down rapdily.... and as such isn't taken up into the fish flesh to any great extent... (your plants will actually enjoy the Potassium).... so unless you eat the fish within a day or two after treatment... they'll be fine...

As EB just posted... Melafix is a different story... and one of the reasons I wouldn't recomend it...

Thanks again, preparing myself for an either larger hit to the system. Rup, after this treatment though, I still can't be sure that my fish won't be carriers of the disease?? Or can I?

If I am salting my whole system at 6ppt for a 3000 litre system I would be needing 18kgs of salt? And with the Condes Crystals at 2ppm I would be looking at 60grams for the 3000 litres? Does that sound right or am I still failing math?