Dart Den

I have noticed a strange film on the surface of the water. Should I change the water more than once a week ?

It sounds like a protein build up. I would not only do more frequent partial water changes but examine your feeding practices as well. Either reduce the amount your feeding or change foods. Clearly the tads aren't eating all the food and it's rotting and fouling the water.

Are you sure you aren't seeing an "OIL type" issue ?

Film = thick, gooey. Def bad.

Oil = glossy, thin, "shimmery". = ok. Possibly tannins released from your piece of leaf.

I would say closer to oil shinny looking

Tannins. You're fine. I have them all the time from the Indian Almond leaves.

Yes
Here is a phone picture
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For what its worth I will give my two cents. I never change water in my tad cups. Just add. I always put a few oak leaves and chuck of Indian Almond to keep acidity high. I have noticed the slick and as Phil said its prob from oil in the leaves and dust or even the muck that builds up. I don't keep lids either, so have to constantly monitor water level, but I prefer the water to breath. The tad cups also collect loose FFs, whose carcasses seem to enhance the growth rate and health of the tads. The more loose FFs that end up in the tad cups are fewer to crawl on my legs when I relax on the couch. I also drop Spirula flakes once a week. I have morphed too many tads to count and never had issues. I am careful to not use house hold sprays etc. I clean house w natural chemicals like vinegar or ammonia... old fashion.

Keep us posted.

I have been doing my once a week turkey Baster water change
I feed only one tad pellet a week
They don't eat it all right now so I feel I'm doing well
I have not lost any

I would vary the tadpole diet and add a tiny bit more food as they grow. When they get really honkin' big -look out. They will chew thru an Almond leaf for a midnight snack.

I always like to make sure I rotate from algae/ spirulina in the food routine and never just tadpole bites.

Tadpole bites are 'ok' but I would never overfeed them, or use them solely.

I do have java moss and the almond leafs as well

I mix the tad bites with spirulina

I should also confirm I use Hikari Discus Bio Gold pellets for protein and fiber as supplement. As much as I kid about FFs, they really do drowned in the tad cups, but not always at a rate that can satisfy the tadpole needs, so I always drop a few pellets a week as needed.