Use more. i give the bottle a good squeeze.

I would use some chlorine bleach to kill the bloom . Keep the fountain covered so no critters can access it. Keep it ciculating for several days until you can no longer detect any smell of chlorine ( or get a pool test kit to make sure it’s all dissipated.). You could do the same with chemicals made for swimming pools. A pool supply store could advise. After there is no longer any detectable chemicals (Chlorine dissipates fairly quickly, especially when aerated) then flush it with fresh water. Then you can begin using the critter safe treatment to keep ahead of it. Put out some bowls of fresh water for the critters while you’re treating the fountain.

This links has some info about shock treating a well with chlorine and testing and dissipation. https://waterfilterguru.com/how-long-does-it-take-to-get-chlorine-out-of-well-water/

@upstatem OK. I guess im just so scared to hurt my critters!

@upstatem Does the company have a website? i cannot find it!

If you can completely secure the fountain (maybe wrap or cover with black garbage bags, get some test strips (mentioned in that article) so you can make sure the chlorine is all gone before you give them access. Even if you just run it for a while after treating it, so the chlorine gets all through it to kill the algae, you can then turn it off and just let it set. I have a fountain with an underground reserve that's 300 gallons, I think, and I do it once in a while, then use the safe stuff to maintain it. The safe stuff won't kill that much algae, but can keep ahead of it, if you start of clean. Do some research so you feel confident. I can't tell how large your fountain is, but if it's small enough you might be able to just put a black yard waste bag over the whole thing and secure it at the bottom, Make sure no water can leak out. You could treat it. turn it on and stand next to it to keep away all critters, so the chlorine circulates fully, then turn it off and cover it. That way no water will drip down the inside of the plastic covering it.

I've read that after you clean the bird bath you add pre 1982 pennies to help retard algae growth. 7 for an average fountain. The copper doesn't hurt the birds.

Shut it down

Clean the pump filter

Fill the bath with 1/2 -/1//2 white vinegar and water

Let that sit for a day, cover the entire thing with a big plastic bag.

Scrub the living daylights out of it

Rinse the daylights out of it.........

But UNLESS you clean the filter (and it could even need a new pump.....)

The bacteria left behind in that bath by the birds and other critters will soon draw algae again.

@JAN MOYER ya know, ive had the pump for like 10 years!!! you may be on to something!!

@JAN MOYER I bought a new pump. however , the clear tubing is original and unaccessible as it is a very very heavy fountain. so I should just leave the original tubing? no other choice i believe....

@Olychick a test kit like this? https://www.amazon.com/gp/product/B09MSY8BLB/ref=ox_sc_act_title_1?smid=A2OA9WXR46U8U4&psc=1