Today I notice some oily spots on the top of the water. Any insight what's that about?
welcome to the forum
It could be from a number of things - not enough surface agitation, low quality food, something that was on your hand. Surface agitation is most likely, but the food can have an impact too. Especially flakes. You can use a cup to remove it, or I've heard of people using paper towels.
is it harmful? Can I just leave it be? I did stop using my air pump for the last few days. i regularly use Tetra flakes, but I fed them hikari frozen blood worms yesterday. It seems to come and goes, this time i just noticed it right now.
It interferes with the gas exchange, since it changes the surface tension - so the water will have a lower oxygen content. If it's not that bad, I wouldn't worry about it....but if it's covering a lot of the surface, then I would.
I would look to change foods, to something of higher quality. Pellets are good because they don't breakdown like flakes do.
Perhaps a Fluval Surface Skimmer would be something for you to look into:
There is another model of the same skimmer for other filters that I use. They do a wonderful job keeping the surface area scum free.
Surface skimmers work very well - they keep the surface clean which helps to keep the oxygen levels up in the water. I have them on most of my tanks.
i've also seen this present when there was a dead fish (but hopefully not in your case!).
I always keep my equipment running - the fish get used to it and come to depend on it.
You can temporarily remove it with absorbent paper placed flat on the surface and immediately taken off and disposed of. Something like kitchen paper or toilet paper works well. Better out than in!
Well the day after this post, one of my angel did die, now the other looks like it's about to die too.
One thing I notice is that my water ph used to be in the upper range 7.6, now it's in the lower 6.0. I wonder if there's anything to do with anything.
I'm wondering if there's anything I could do in the mean time.
Sorry to hear of your troubles.
pH of aquarium naturally becomes lower (more acidic) over time as buffers are used up - usually combated by water changes.
You may have a water quality issue.
I suggest checking the feeding is not too much, checking the filtration is top notch and that water changes of 20 to 40% are being done weekly.
Is there sufficient biological filtration?
If your ph crashed, I recommend checking your GH and KH levels. They make a GH/KH liquid test combo pack you might be able to find. Low GH or KH can cause this.
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