Backyard Aquaponics
A place to discuss aquaponics

Hypothetical time.

Ok, so lets say you have a new small system, with no ability to isolate GB from FT for any significant length of time. You have no separate quarantine tank. And you have no other possible place to put your fish, then in their current tank.

And then lets say you have some diseased/infected young fish, like 15cm and under. And you have 100 of them or less. And the you who have to assume that the water they swim in is infected (I guess). A combination of a very poor supplier (and the fish were mostly infected before they came to you), and multiple causes of stress on your fish (like very rough transportation, extended exposure to low water quality, low DO etc). You are getting daily deaths

You cant salt beyond 4-6ppm due to the fact it will kill your plants, and thereby make your water quality even worse (or will it?)

Do you:

A) simply salt to 10+ppm and see how your plants go
or
B) do a complete kull of the remaining fish, plant them under a new fruit tree, do a total water purge, refill with fresh water, and restock with fingerlings?
C) salt to very high levels, immediately plant out any spaces you have with salt tolerant plants (and remove any casualties) and see what happens?

Salt bath treatments of 10-12ppt.. are typically only done for periods of between 1-2 hours max.. although have heard of hem being down for longer....

But then they're reduced to around 4-6ppt.... so you could salt your tank right up.... then do a 50% change... and follow that by another 50% change a few days, or a week later... etc..

Overall, not a good scenario. I will assume that the water is otherwise testing ok for ammonia, ph and nitrites. Water quality is a common culprit. One thing to do where you can't go wrong is to aerate the water to the maximum of your ability. You cannot put too much air into the system. Even if you do a total water change and turf all the fish, parasites will in all likelihood still remain in the system.

Salt can only do so much, and in higher concentrations, as you know, will kill some/all plants, may not save your fish, and may actually cause the death of the fish. The course of action really needs to be dependant upon what is the underlying problem with the fish, as some treatment will not help. Salting is cheap and easy, and is generally considered a good propholactic treatment for salt tolerant species (some catfish for example can't tolerate salt), and does help reduce stress in fish in low levels. Salt levels up to 0.6% is generally safe for many fish, but once again, it depends on what specifically is wrong with them, and this level will kill many plants. Is there any more description you can provide on the dead and suffering fish? Some types of parasites (like trichodina) will clear up with a salt treatment, and about 7 of the 9 most common parasites will clear up with salt. The ones that do respond to salt, will generally respond to a 0.3% dosage, so going higher could be counter-productive. Flukes will only marginally respond to salt however (about 40% of the time). Dosage at the higher levels than 0.3% probably won't really help you much. The good thing about salt at the lower level is that it won't harm your bio-filter.

WARNING- this is not a recommendation. In years past, I have had excellent results using potassium permangenate(PP) (where salt failed) in dosages up to 4 ppm (only 2ppm for young and scaleless fish) in treating a variety of fish disorders, like flukes, fungus, and even with antibiotic resistant strains of aeromonas hydrophila. It does however require extremely accurate pre-analysis of the biological load on the water, and it will kill the bio-filter if it is circulated through it before it has become inert. You will need to isolate the growbed, assuming that is your primary bio-filter. It will only need to isolated for 24 hours however. It is not for arbitrary use, and if not used correctly, will kill everything except the plants. If used correctly however, it can be an extremely effective and cheap method of last resort only. It is not for the timid or mathematically inept, and needs to be done exactly correctly. You would need to know the exact water volume and determine the biological load for example. I can impart the detailed procedure to you if you require by sending me a pm if you are desperate and can obtain a small amount of PP.

Good luck

Good point to note regarding catfish....

Yes, potassium permanganate could be used, and often is in aquaria systems with ornamental fish... and was occasionally used in aquaculture...

As is Formalin.... but neither (as noted) are treatments which I would advise for the average backyarder...

Even salt dips or baths.. which must be done with high oxygenation and constant monitoring... are usually unnecessary except for open infected wounds, ulcers or heavy bacterial infections...

Most other symptoms .. like fungal issues, fin rot... will respond to 6ppt quite adequately...

And parasitic infestations.. like Ich... can be treated with 3ppt... if caught in time...

What exactly is your problem???

P.S... IMO... you should salt to 1ppt whenever you introduce fish...

Thanks for all the comments...the above hypothetical was a slight exaggeration of what Im actually dealing with...

Ok, well I separated the GB's from the FT for a few days (have been adding more GB's and adding interconnected sumps, so had to anyway) and then salted to about 6-8ppm. I did daily 50% water changes and re salted to these levels...Since doing this (and my original post) I have no no deaths, which is wonderful.

The deaths that I had before this (all except one, which Ill come to) exhibited no visual signs of parasites or disease...the one that did show symptoms (that I noticed and subsequently posted about, and got very scard by the reply...) were as follows

One fish (Nile Tilapia btw) was at the bottom of the tank for hours and hours just swimming in tight little circles...when he finally died and floated up his body was locked in this curved form that he had whilst circling....it was suggested that this was Streptoccocus, hence my queries about a total water purge.

No fish before or after has been noticed doing this, and certainly no dead fish were locked in this stiff curved shape.

I have one of two fish that seem to be of a much lighter colour then the others, with noticeable white patches (not spots...its not ICH). One has a large whitish patch on the head, the other near the tail...other then this they seem perfectly healthy....

My guess is as follows....the poor things have been stressed beyond belief....
My colleague bought the fish before we even had any where to put them...they had a very rough, very long transportation period, and then were introduced into very poor water. Oh, and the supplier was rather dodgy and there were alot of dead fingerlings in his tanks....

it has then been a case of getting the system just right, and everyone was happen, then he powers that be decided they wanted it expanded...so there has been more stress while we have been messing with their tank etc, and for a while there was insufficient aeration....

So basically, it has been very high stress levels either killing them directly, or cause other issues to take hold....

So following my logic....if in the future I were to introduce healthy fingerlings after a quarantine period, that didnt have such rough transporation, and the system was healthy and established (even though its the same water as before i.e with the potential parasites existing etc) they should be ok because their immune systems etc would be tough enough????

Cheers.

floyd.