Not really enough info to know...but in general the bubbles are caused by very small particles which act like soap. Scooping out the foam removes some of the particles because some of the particles are in the foam, they form the foam. But just like soap removing the foam only reduces the material.

Whether the stuff effects fish and how long it lasts depends on what the stuff is, which can't be known. The assumption has to be it was from something in the filter.

I often rant against these types of filters and these kinds of sellers for many reasons. In this case the seller wants the cash and tells you to wait out the foam. And he may be right. The foam will likely go away at some point. Maybe it out gases into the air, maybe it reacts with stuff in the water, maybe it breaks down into other elements in the water. Who knows? Sure doesn't sound like the seller knows or cares what the stuff is. He's gambling your fish won't be killed, which is a pretty good bet.

The question I have for these type of sellers is...How can you sell such a piece of crap? What right do you have to gamble with my fish? It's a bio filter. It's suppose to reduce waste, not add it. Is that what you paid for? I don't like being scammed and would return the filter and vow never to return to that seller.

The second thing is a bio filter has nothing to do with making water clear. Bio filters convert ammonia and nitrite, that's it. A UV filter clears green water.

So maybe this filter has a UV too? That would fit clearing green water in 3-5 days. But that requires a proper flow thru the UV and 1600 GPH sounds way too fast for a 250 gal pond. But that depends on different things.

You don't say how many koi you have or whether you're testing ammonia...but just as a heads up...green water algae consumes ammonia directly meaning it acts as a bio filter. A very good bio filter. If you have a UV this algae may soon be dead, actually probably already are dead (takes a few days for them to decompose and then water clears). If all this is the case you may see a jump in ammonia in the next few days depending on number of fish and amount of food fed. You want want to consider testing ammonia.

My standard rant...
I don't know what kind of bio filter this is but I'm betting static submerged media (pads, balls, whatever stuff that's under water and doesn't move)? These filters are very poor bio filters. I consider them worthless. That's just my opinion of course but I can tell you this, there isn't a single serious koi owner, koi breeder or fish farmer in the world using this type of bio filter. At least not for the last 15 years or so. That's because much better bio filters were developed in the last 15 years. Trickle Towers, Moving Bed, Bakki Shower filters have been tested (years ago) and found to be at least 30 times better at removing ammonia than static submerged media. These static submerged media filters are very cheap to make and are only sold to newbies. And I think that makes sellers of these very dishonest. But that's just me.

I understand you hate canister bio filters. Worthless, I know. But I am missing a piece in your argument to understand your position fully. You seem to be saying bio filters don't get rid of green water? But suspended algae feed off of Ammonia, which is why it can function as a bio filter. Other types of bio filters also reduce ammonia by converting it to nitrite and nitrate, including moving bed, trickle towers and canisters. Without the ammonia as food doesn't the suspended algae go away? What piece am I missing? Plants, such as WH also remove ammonia and help clear the water. Until 2 years ago I always had a clear pond after a few weeks of running the filter in the spring and I never had a UV until now. So I know I must be missing something or misunderstanding your position. I know my current canister bio filter won't last forever, but I am not a " serious koi owner, koi breeder or fish farmer", either. So for many who have small backyard ponds of 100-500 gallons like mine and this one, what do you think they/we should be using that is readily available, isn't over sized compared the pond size, doesn't require a contractor and can be concealed fairly easily?

cwjudd,
I have a biofilterm works great. It's not the filter itself at all.
What is that red stuff in the pic? Just wondering.
Just wait a day and see if it clears up. Mabey it will go away.
If not, just come back here on this forum and post an updated pic again, I am sure someone will be able to help you.