Fish Scraping Themselves Against Substrate

[DRB]

G'day again all.. geez it seems this part of the forum is my most active as of lately!
 
So, my Kribs (and I noticed a Cory do it today too) have been rubbing themselves against the substrate.. It's not a constant thing, just something I have noticed over the last few days happening more often than usual... I know that this can often be a symptom of Ich, however I just wanted to ask a few questions before I freak out and medicate/raise the temp.
 
Ok so first of all, The Kribs have always seemed to do this here and there, and I've had them for a few months now with no illness or Ich/Whitespot.. The females seem to do it, not the male, and often they will suck up some gravel and then quickly flick their sides against the ground, or other times just flick and no gravel sucking. Like I said it's not a constant thing, but I have noticed it happen a few times today.
 
Today I also noticed a Cory kind of do a similar fast little flick with their side against the substrate as well.
 
None of my fish have any other symptoms of Ich/Whitespot, they are all active, eating well, swimming around most levels of the tank, and not really hiding away. None of them have any actual spots of flakes of Ich on their body either.
 
So I guess this is a pre-emptive emergency post... should I be worried about this body scraping by itself? Would it only be Ich if the spots had already appeared?

 

[snazy]

Do more water changes mate. The tank may have trace ammonia levels that annoy them. They are often not detected on the liquid tests but my fish used to do that when I cleaned the filter really well possibly causing some raised ammonia levels. Other possibilities I've come across is them trying to dislodge some stuck gravel/sand in their gills if they are sifters. Also of course some other possible toxin or parasites of some sort but if you can't see any other signs, hold off and just do at least two 50% water changes for the next week or two and see how they get on. Don't overclean your filter in the mean time just in case you reduce the good bacs. Hopefully it's nothing to worry about. Also, dechlorinator with aloe used to annoy my corydoras the same way immediately after water change.

 

[DRB]

Hey Snazy thanks for the reply
Well 2 days ago I did switch my filter over to a new Fluval 206 (filled it with all the media that was being used, and squeezed out old filter sponges so hopefully no need to cycle again), but that sounds like it could possibly cause those trace level irritants. 

Some water changes sound good, I do 25% every 2 weeks as it is currently, but maybe two 50% like you say would be a great idea.

 

[snazy]

Yes, more water changes will certainly help. See how it goes after a week with larger regular water changes. The irritation should stop if it's water quality/toxin issue and of course your filter will pick up fast too helping the matter. If they improve(they should), then I'd say it's better if you manage at least 50% weekly. That works best for me unless the tank is heavily planted or very lightly stocked. Also, better filtration to cope well with the levels will help as well.
At the same time observe for any other signs like stringy poop, caved in stomachs, refusing to eat, hiding in secluded corners or separating from the group, external signs, etc...just to be sure it isn't something else too.
When my fish did it, the scratching always stopped in about 2-3 days after cleaning when I suppose the filters regained their efficiency. I don't clean more than one filter at a time now and I never touch the bio media, just the mechanical media as a precaution and I haven't seen it happen since. But it did happen once in another tank I have that was cycled but I increased the bioload too fast. They again stopped in a few days when the filters caught up with the extra fish and haven't done it since. So I think ammonia is to blame, even at very low levels.