Flashing/scratching

[andyroo]

Wise folk,
Can you provide a quick run-down for the (potential) reasons for flashing/scratching?
Might be good for a "Sticky"
Thanks
A

[Diana]

Basically it is irritation from some cause, usually external.
Parasites of many species can make fish flash. The pests may be inside the gills, and not visible, but this still counts as 'outside the fish'
There may be water quality issues; pH, and ammonia, I think, are the biggest two causes, but I am sure that other chemicals could do it, too.
Medicines may be irritating to the fish.
Other signs of irritation may include excess slime coat production.
Hints that the problem my be in the gills might be fish that flash, and also gasp for air, or breathe heavily.
Toxins in the water affect different fish more strongly than others, and you may see a range of symptoms, depending on the actual toxin.

If I saw fish flashing I would do a few things:
1) Observe the fish.
Can I see an obvious parasite?
Are there other behaviors that might hint at what is going on?
2) Water change. Toxins and some phases of certain parasites can be removed from the water with water changes and gravel vacs. If I suspect a toxin I might do a couple of really big water changes and add activated carbon to the filter.
3) Test the water with all the tests I have to see if anything is off. This is not limited to the aquarium test kits, but look and smell the water, too. If you think someone may have added something to the tank you might find traces of it on the lid. Ask in the household: Did anyone do anything with toxins that could affect the fish? Aerosol stuff is notorious for this. (I lost some fish when my daughter used some hair spray in the same room.)
Did someone overfeed the fish leading to an ammonia spike?
4) Continue to monitor the fish, even if the flashing goes away. There still might be something going on.

[chefkeith]

Flashing can be caused by suspended solids also. These solids individually are too small to see with the naked eye. A micron filter, a canister stuffed with filter floss, or a diatom filter are a few good ways to remove suspended solids. Of coarse, water changes help too, but water changes will only get rid of that equal % of the solids.

I use the micron quick filters and filter floss at all times. Diatom filters are excellent, but can be a pain in the butt to set-up and operate.

[Holdstrong]

I am not nearly as experienced as some of the others on the boards. But here is a recap of my struggle with unexplained flashing.

I've had flashing off and on in my new 75g tank since I set it up. Which is pushing 4 or 5 months now. (the filters and fish are a lot more mature, the tank is just new)

Water perams have always been perfect. 0 across the board (it is understocked, gets lots of changes, and has plants). PH steady.

I've gone back and forth on freak outs over this. Many a night I have been in there with a flashlight trying to spot the first ich spot, lol. Some days I am convinced the fish are not getting on with the tannins from some of the new driftwood. Hell, some days I am even convinced the flashing increases after water changes... but this is the same tap I have used with these fish for years - so I might just be imagining things.

I even dosed the entire tank with Flubendazole (from inkmakr) because I have had a skinny loach for a year+ who isn't beefing up and though that maybe he had a parasite or protozoa that was finally starting to get at the other fish. But no change came of that.

My favorite theory, I was convinced at one point it was cat hair. I have a big furry Himalayan who is in all out shed mode and try as I might I can not always keep it out of the tank. I thought maybe some of the fish were getting strands caught on them and the flashing was trying to get it off of them. Ha!

I still don't have an explanation, but Chefkieth's mention of suspended solids seems as good a fit for my situation as any. New tank, few new decorations, I'm still not sure the two cannisters I have are cutting it, etc etc. There very well could be a suspended solid issue.

[Diana]

Holdstrong, you could add some polyester floss to the filters in hopes of trapping more fine debris. Not as fine as a diatom filter, and probably not as fast, but certainly your filters should catch cat hair (even without floss). I have a similar problem with a dog that sheds your round, but I find almost no dog hair in any tank or filter. (Behind the tank stands, next to the wall is another story!)