Pristella Tetra Problem

One of my Pristellas has been swimming oddly for a week or so...  Almost impossible to capture on film, but he/she is swimming at a tilted upwards angle when in a relaxed state...  As soon as food is around, the swimming is back to normal as it is if the fish needs or wants to move suddenly...  But when just chillin', then there is this uphill looking angle of maybe 25 degrees or so, as if the fish is unable to just remain stationary...  Any clues peeps...?

Here's a little video clip, although for some strange reason, the problem looks a lot less bad in either clips like this or in photos... 

This often happens.

In the first instance, what I would do is to ensure that you eliminate the possibility of any internal blockages which might in turn be pressing on internal organs such as the swimbladder (the fish's buoyancy aid). To do this, increase the proportion of non-dried (flake/pellet) food by feeding pea (shell off, each half chopped into tiny morsels), brine shrimp or bloodworm, which ought to induce an intestinal "clearout" if need be.

If the above doesn't improve the situation after a week or so, or the situation deteriorates in the meantime (or the particular fish stops eating, starts lurking in a corner or otherwise behaving oddly, or develops additional visible problems), let us know and we'll provide further advice on what to do next.

Also take a look at the base of the pectoral fins - sometimes a fish which has had trouble swimming and maintaining its buoyancy can result in having inflamed bases of the pectoral fins (as I discovered in my own pristella/x-ray tetras), and I also suspect that the converse can happen ie a fish with a damaged fin may have trouble swimming and potentially end up swimming off course such as in the manner you describe. If you notice anything unusual in the fin bases, let us know too.

Hope this helps, at least for now.

Mrs Cookie did wonder if it might be pregnant, but it doesn't look swollen or bulky etc...

"Birds and the bees" info for Mrs Cookie - non-livebearing fish don't become "pregnant" as such but instead lay eggs which the males swim over and fertilise. (Livebearers are guppies, mollies, platies.) In my 3.5 years of having female pristella/x-ray tetras (sadly, both females have now died), I never saw eggs released - and that's with considerable time spent with the fishtank in front of me but I did witness lots of "activity" taking place among the plant leaves (on occasion, a female with all 4 males at once!). Fish can become egg-bound but, if the fish isn't looking swollen/bulky, it doesn't seem as though it's that.

If the scales start to stick out like a pinecone (there's no mistaking that when you see it - this is dropsy), then definitely treat ASAP at that stage with eSHa 2000 or Waterlife Myxazin in case it's caused by a bacterial infection. However, there's nothing in what you've described so far that suggests the need to treat, so let's see for now how the fish responds to the dietary change. Presumably you've tested the water too for ammonia/nitrite/nitrate levels?

The plants will help a lot.

Once the tank is mature - six months after completing a cycle - you can start testing less frequently, though it is good practice to test for a few days every time you add new fish even with a tank that has been running for years.