Backyard Aquaponics
A place to discuss aquaponics

I've noticed some small patches of white fungus on my perch that resemble cotton wool. These are adult fish that I purchased a few weeks ago from a local fishmonger, so they were living in pretty dire conditions. Had a search around and it looks like 'hyphae' fungus. there's plenty of medications and treatments available but I've heard that some of these preparations can't be used on fish that are destined for human consumption.

Anyone had experience with fungus? And if so, what was the best treatment?

Saprolegniasis refers to disease caused by several genera of opportunistic fungi or “water molds” that infect the gills and/or skin of aquatic and larval amphibians. When in water, newly affected animals appear to have a whitish cotton-like growth on their skin. As the fungal mat ages, it may become greenish due to the presence of algae. Once removed from water, the fungal mat collapses and is difficult to see. Other signs include lethargy, respiratory distress, anorexia, and weight loss. Skin ulcerations may occur as the infection progresses. A diagnosis of saprolegniasis is made by finding hyphae and the thin-walled zoospores in a skin scrape. Treatment with a malachite green dip (67 mg/L for 15 sec, once daily for 2–3 days) or copper sulfate (500 mg/L for 2 min, once daily for 5 days, then once weekly until healed) may be effective. Treatment of eggs with methylene blue may be effective. Secondary bacterial and parasitic infections may be present in animals with dermal ulcers. Poor water quality conditions should be corrected.

Hi
The above is a copy and paste job from Merck Veterinary Manuel.
Potassium Permanganate KMnO4 is also widely used to treat fungal infections.
Historically it was used “to disinfect drinking water”
BUT be very careful!
You need advice from someone with more chemical knowledge than I gained Googling
Titus

Thanks Titus!

The veteterinary instructions above would generally not be advisable for fish you plan to eat.

The malachite green is a no no with edible fish. It stays in the flesh after use, and can cause issues when eaten. It's banned in commercial aquaculture setups with edible fish.

You can either salt the whole system, or move the fish to a quarantine system, and salt that system.

OK salting sounds like the best option. How about dosing for a 1000-litre tank? And how long would I need to continue treatment? Will salting have any effect on microbial communities in the filter medium?

One kilo per thousand liters gives you 1ppm you want 3ppm so three kilos should do the trick,salting at that level will not harm your bio.

Great. Thanks Dasboot.

Hi
I did some more reading on this subject and got into 37% formaldehyde ( formalin) dips. No! I wouldn’t fancy eating the fish after this either!
But what caught my eye was, “freshwater dips”
Your fish are in say 3ppm saline. You then dip into ‘fresh water”.
This is claimed, ‘to reduce mucus and flush parasites’
Your fish are stressed anyway. This is safe. ( to eat the survivors) Cheap and easy to do.
Any thoughts?
Titus

If it is a fungal thing
Salt to 6 ppt, stop feeding and run your pump 24/7, some of your vegies wont like it but you might save your fish.

Yeah I read about salt bathing a couple of times a day in a strong solution for about 30 minutes and then returning them to the fresh water. Sounds a bit laborious, though.

I'm gonna dose the whole tank at 3ppm and see how that goes. Pump is running continuously and I've stopped feeding.

Thanks everyone for your feedback.

Titus i believe this works on osmotic regulation, if your parasites are in 3ppm salt or higher they are internally at this level,by bathing them in freshwater,the saline insides wants to migrate to the freshwater and the parasites rupture and drop off the fish.
The formaldehyde and malachite green treatment are very popular and effective in the world of koi keeping and as you don’t eat them its ok to use.

Osmosis - the diffusion of water (across a membrane)
Water will move in the direction where there is a high concentration of solute (and hence a lower concentration of water.
A simple rule to remember is: SALT SUCKS
Salt is a solute, when it is concentrated inside or outside the cell, it will draw the water in its direction. This is also why you get thirsty after eating something salty.
 
Type of Solutions
Isotonic Solutions
If the concentration of solute (salt) is equal on both sides, the water will move back in forth but it won't have any result on the overall amount of water on either side.
"ISO" means the same

Hypotonic Solutions
The word "HYPO" means less, in this case there are less solute (salt) molecules outside the cell, since salt sucks, water will move into the cell.
The cell will gain water and grow larger. In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting
In animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES will pump water out of the cell to prevent this.

 
Hypertonic Solutions
The word "HYPER" means more, in this case there are more solute (salt) molecules outside the cell, which causes the water to be sucked in that direction.
In plant cells, the central vacuole loses water and the cells shrink, causing wilting.
In animal cells, the cells also shrink.
In both cases, the cell may die.
This is why it is dangerous to drink sea water - its a myth that drinking sea water will cause you to go insane, but people marooned at sea will speed up dehydration (and death) by drinking sea water.
This is also why "salting fields" was a common tactic during war, it would kill the crops in the field, thus causing food shortages.

Diffusion and Osmosis are both types of PASSIVE TRANSPORT - that is, no energy is required for the molecules to move into or out of the cell.
Sometimes, large molecules cannot cross the plasma membrane, and are "helped" across by carrier proteins - this process is called facilitated diffusion.

Hi
Thank you for that Dasboot.
I like the simplicity and safety of ‘freshwater dips’

Titus

Second week of salt treatment seems to be going well. The fungus has disappeared but the fish are still rubbing themselves on the driftwood, or 'flashing' as some refer to it.

Ummm... I believe that some fingerling suppliers use FORMALIN..
Had I heard FORMALDEHYDE, I would have raised concern... ie.. It did not click, that FORMALIN was the same toxic beast..

SOooo... If fingerlings were bathed in FORMALIN, what is the likely issue for grown fish..

I think that I heard the thought that FORMALIN was approved for use with table fish.. I seriously wonder how that could possibly be.
..
.