As I said in response to your email...
Google "pond pH buffering", read, learn, then do. Often people go to forums to get a fast, easy solution...bad idea.
I have no idea if your fish will live through this, they might. Depends on what shape they were already in. I do know this for sure, if you keep doing stuff based on what people tell you without understanding the basics you will kill your fish at some point.
I don't do phone consultation any more because it rarely helped people.
In your case you the biggest risk is ammonia. At 5.0 pH ammonia isn't toxic to fish, at 9.0 it's very toxic. So if you had any ammonia level you added that problem to the sudden pH change.
The good news is just because you measured 5.0 pH once doesn't mean a few hours later it wasn't 8.0. Water that isn't pH buffered means the pH swings up and down. If these was the case then adding the baking soda and increasing pH probably didn't do more harm.
You measure KH to know whether more baking soda is need. The 2 lbs per 1000 gal is just a starting point, a good starting point if KH is very low. Once you have KH in a good range you have to keep measuring and adding or you get another pH crash. My point is...this isn't difficult, but it isn't as easy as picking a few things out of a forum. You actually have to have some basic understanding.
i am in manalapan 07762 . i am consulting pond department people at brock farms on route 34. their worker who claimed to have a degree in ecology did the water exchange etc. additional worker prescribed paracide green for my fish upon seeing them. he however admitted that whatever he knows he learned on the job and via consulting the web. could you please provide me with info re the place you use.
tx a lot
Here the basic problem...and it's always true. When I take my car in to be fixed the mechanic gives me some options. I know nothing about cars...how in the world can I possibly make any kind of rational decision? Sounds good to me? Cheapest?
When asking for fish keeping advice it's the same problem. I've seen it many times, maybe 95% of time, the poster will choose the worst possible advice or pick bits and pieces of advice and make things worst.
My absolute best advice...and almost never followed...is to do nothing. Fish stand a much better chance on their own rather than having cure after cure thrown at them by an owner frantic to cure something they don't understand. Learn first...do later.
Where to learn...
Forums are a good place to get subjects to research, but really bad places to learn. In forums you get opinions..."well I did this and my fish are fine"...meaningless beyond maybe a subject to research further, but rarely are any actual details given to research. Without basic understanding a person has no hope of telling good advice from bad. And bad advice is almost always simple, easy to understand, sounds kind of logical...so the deck is stacked against you. The only way bad advice can survive in forums is if it sounds good. There are serious forums like Koiphen. A good place to read but not so much to just post questions without having done any research. They tire of "My water is green what do I do?" questions. Most pond forums are more of a social or entertainment deal. Really great for what they are.
It takes a lot of reading and an ability to weed out bad info. And maybe 80-90% of the info out there is really bad, fish killing bad. It wold be great if there was just a few good sources, but the internet has done away with that concept. Now anyone who can type is an "expert": The more you know the easier it will be to spot BS. If the info you find is difficult to read it's probably a good source. Never trust one source. Compare and research differences. Understand the why, then you'll understand the doing.
Basics...
Understand there are different kinds of ponds. Many things will appear contradictory otherwise and make no sense. For example, plants in a Koi pond is generally considered a very bad thing by high end keepers. While in a Water Garden plants are considered essential. Contradictory if you just pull that one point out of text. If you instead understand why each source is say bad or good you'll understand they're both saying the exact same thing but for different goals.
Google "pond pH buffering". Pretty easy subject. Stay away from all sites that say egg shell, plaster, oyster shell can be used for pH buffering...they don't understand anything. Oyster shell have benefits, but not for pH buffering. Stick with sites that use baking soda. When you understand why knowing a KH level means you don't have to know pH level you're probably understand pH buffering.
Google "pond ammonia". After you understand where ammonia comes from, how to test it, and how it's removed from the pond you're ready. For an advanced topic Google "pond ammonium vs ammonia". When you understand ammonia toxicity is effected by temp and pH you'll know more than 99% of pond "experts".
IMO that covers most of what you need to keep fish alive. Seriously.
There are a bunch of videos done by Dr Johnson at
Koi Beginner that I think are a very good starting point. And again, if you watch every video a couple of times, research some of what is said so you really understand it, you'll know far more than almost any "expert". I don't agree 100% with every tiny point Dr Johnson makes, which doesn't mean I'm right and he's wrong, but I think it's a great resource.
