Backyard Aquaponics
A place to discuss aquaponics

Hello,

My silver perch all died over several weeks due to disease. It was hard to work out what disease,so I am not sure.

Definitely one had patches of white, others excessive mucus and looking pale.

What I am wondering is do I have to get rid of the water or can I reuse it, or clean it?

Hiya Quinny, my understanding is that most parasites require a host to survive.
Buuut back to your fish issue, how do you believe the pest was introduced to your system?
Did you salt the water?

Hi Skeggley,

I am really puzzled trying to figure out what brought this on. Some fish had been in there for about 21 months and the others for 9 months.

My best guess is some combination of the larger than usual amount of rain we've been having, cold temps and maybe over or under feeding (because I use sinking pellets and it's hard to see if they all get eaten - but that's how I have always done it).

The flow of water from the growbed had slowed too but I didn't see any issue with dissolved oxygen (like fish coming to the surface).

No I did not salt the water.

Would salting the water be enough to "cleanse" it?

Fish constantly live with the parasites. Their curclitory system is open so to speak. All it takes is a bit of prolonged stress for the parasites to take root and explode. Once the parasite load goes past what the fish immune system can handle you see the affects on the fish. All it takes is one fish to get sick. Then you get a parasite boom. Happens sometimes with introducing new fish. Or sometimes your tank could have a parasite your fish are immune too but it kills the new fish because they were too stressed.

It would be best to know for sure what the ailment was. Then you can safely say whether it safe to just drain and replace water or sterilize and start over.

Personally I have only sterilized and started over once because of Ich. That was horrible. If you are sure it wasnt an annoying illness like Ich. I would drain the system and refill. Then keep my bio filter alive with ammonia until i got more fish.

You could salt the system as high as high as the plants can take. Then after a day or so drain and flush the system as kind of quasu sterilization to preserve your bio filter and plants.

Salt it great medicine for illness. That rapid rise in salinity causes the parasites to explode. Keep the salinity low enough and it wont affect plants. A lot of ailments can be treated that way.

There are methods to salt dip new fish before adding them to the tank to ensure everyone is sterilized. I successfully pulled it off last fish addition. But it was time consuming all day process with the drip acclimation. Then salt water dip before being let loose.

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There are many fish diseases that cause similar signs. Often the only way to know the cause is to send them to a pathology lab for diagnosis. That being said, many times it’s water quality issues that stress them the most. I seem to remember that a period of about three weeks without fish will result in death of most parasite larvae left in the water.

As the others say stress is a key factor. All I watch now is the system pH and with the rains I see the pH drop so if you haven’t, check your pH. Perhaps look at floating pellets in future, https://www.cheidysaquaponics.com.au/pr ... fish-food/ are well priced and have free delivery. I always aim for the underfeed scenario and with the cool temps silvers don’t require as much food. The build up of uneaten food on the ft floor ain’t good.

Yes salting would have been beneficial, it helps the fish build a slime coat which is a parasite defence. Long ago I had, what I call, an ich issue, when I got fish from another system. Furry fungus looking stuff that made the fish skin look like it was peeling off. This was on trout and advice from this forum was to salt which I did and most of the fish recovered. Fortunately I had 2 systems at the time so used the small one as a hospital tank and the trick was to salt shock the system by quickly raising the salt levels then lowering it and continue this cycle until fish health returned. Only the celery thrived. Still now I like to add a measure of salt every now and then as the fish seem to like it and hopefully it seasons at the same time.

Going forward, check pH, add some salt, maybe 1ppt or 1kg per 1000 litres, wait the above mentioned 3 weeks parasite life cycle before adding more fish, get your fish from a reputable seller and maybe salt bath the fish before adding to your system.

Thanks everyone!

Sounds like a combination of salting the water and draining all the water and filling the tank again.

I like this suggestion the best from Rcmaveric


So I will go with Skeggley's suggestion of 1kg per 1000L of salt, then I'll drain it. I need to clean out the bottom of the tank anyway, as well as the grow bed/media. So I expect I will lose a lot of beneficial bacteria and worms, etc...

The only plants I care about in there are the pineapples. When I clean out the grow bed I will keep a bucket of pond water to put the plants in.

I definitely need to set up a quarantine tank and re-organise my fish tank and grow bed so that I can see the fish better.

While writing this ideas are popping into my head... I think it's time to create some add-ons that I have wanted, like a SLO and RFS and a bell siphon.

Run it through activated charcoal and then use it for you flower bed or yard.

Hey Quinny, constantly running a system with 1 ppt salt is often recommended for fish health and a 3-5ppt is a better shock treatment, I had the trout up around 8ppt when treating.
If you’re going to empty your system I wouldn’t add salt until after you’ve carried out your upgrades so you can use the water on the yard.

+1 to most recommendations. From your description it sounds more like columnaris which is a bacterial infection, not a parasite, but we will never know for sure. Ich presents as tiny white spots on the fish.

As mentioned before you can keep the water. If a couple of weeks have passed then the pathogens have likely decreased significantly or completely. Even if you change the water, if there are any pathogens that did remain, they will still be in the wet grow beds and residual water. So while a water change may help reduce the exposure, it will not eliminate all pathogens.

Once you have the water you will keep, then add chloride salt such as KCl, NaCl, CaCl, etc. at 1kg/1000l for 1ppt concentration. I typically maintain 1.5 - 2 ppt. Anything over 3 ppt may adversely affect your plants. It is best to get a refractometer so you can measure the salt % and know when to add more or not. Otherwise you will be guessing in the future after rains, etc. Be sure to use a pure salt product that does not have any additives. Good sources are aquarium salt (expensive), pool salt, solar salt (water softener salt with no additives), etc.

For a quarantine / hospital tank I typically maintain 5 - 7 ppt salt and at least 27C (depends on the fish, 27C will kill trout). I keep the fish in there for 10 days minimum. It is also VERY important to have fully cycled filtration for the hospital tank so there are no ammonia or nitrite spikes, pH crashes, etc.

Other people use a salt bath, that I believe is 35ppt salt and you put the fish in for up to a minute or two, and remove it before it dies. I've not tried this method but it is common. A Google search will return a lot of information.