Does Seachem Prime Really Deplete Oxygen? Answered

I just read a commeng on a thread stating that the most popular aquarium dechlorifier, Seachem Prime (which detoxifies ammonia, nitrite, chlorine, chloramine, and heavy metals), does nothing but dechlorify and deplete oxygen. But really? This can't be true with how popular it is. So I researched it and turns out, again, they're mostly wrong. When overdosed, Prime depletes a little bit oxygen for an hour at most, or longer in extreme overdosing cases (but why would you overdose so much in the first place?) So here I go again, another myth DEBUNKED by searching on DuckDuckGo for 30 seconds....*facepalm*

 

I have never faced an issue. I use it very sporadically and follow dosing instructions to the letter. Usually only if my parameters are questionable to me at the time. Like a minor detection of ammonia or nitrates over 25 ppm(my guy is sensitive). There is evidence that it does but I looked it up and found the same thing you did. Like any other chemical, used moderately as per the manufacturer’s instructions it is life saving.

 

API dechlorinate is sodium thiosulfate: https://apifishcare.com/pdfs/API TAP WATER CONDITIONER_1625170479.pdf

Prime is the same thing per chemical analysis and its own MSDS.


Here is a thread where someone added dechlorinator to their tank in the normal amount and their oxygen went to low levels per measurements. Results for 2x, 3x dose are included.

Very odd fishless cycle parameters | Aquarium Nitrogen Cycle Forum | 520496

Start at post #25 to see a father patiently cycling a tank, and then suffocating all the kid's fish due to adding Prime. I am quite sick of seeing this happen. It's called a fish kill


OK, here is the way this works. When you add dechlorinator to your tap water, it will reduce the chlorine. But any excess dechlorinator can reduce oxygen. You have to know how much dechlorinator to add to your water so that you are not adding extra.

Chlorination De-Chlorination


So there really is no way they can tell you how much dechlorinator to add since it depends on how much chlorine or other reducible agents are in your water. This creates a lot of confusion when folks try to test how much dechlorinator is 'safe'. It depends on the water being tested.

In aquaculture, when water is dechlorinated, it is always followed by aeration before being used for fish. Aeration is easy.

When water is discharged into streams and lakes, the excess dechlorinator has resulted in fish kills.I have seen it on lake Ontario. Therefore it is practice to control the amount of dechlorinator so there is no excess.

OP, you can grab a 02 test, and then add Prime to your water until you see the oxygen decrease. This will tell you the safe dose for your water. This is 'titration' and is a needed step to control how much dechlorinator is safe to add. But everyone's water will be different.

 

API dechlorinate is sodium thiosulfate: https://apifishcare.com/pdfs/API TAP WATER CONDITIONER_1625170479.pdf

Prime is the same thing per chemical analysis and its own MSDS.


Here is a thread where someone added dechlorinator to their tank in the normal amount and their oxygen went to low levels per measurements. Results for 2x, 3x dose are included.

Very odd fishless cycle parameters | Aquarium Nitrogen Cycle Forum | 520496

Start at post #25 to see a father patiently cycling a tank, and then suffocating all the kid's fish due to adding Prime. I am quite sick of seeing this happen. It's called a fish kill


OK, here is the way this works. When you add dechlorinator to your tap water, it will reduce the chlorine. But any excess dechlorinator can reduce oxygen. You have to know how much dechlorinator to add to your water so that you are not adding extra.

Chlorination De-Chlorination


So there really is no way they can tell you how much dechlorinator to add since it depends on how much chlorine or other reducible agents are in your water. This creates a lot of confusion when folks try to test how much dechlorinator is 'safe'. It depends on the water being tested.

In aquaculture, when water is dechlorinated, it is always followed by aeration before being used for fish. Aeration is easy.

When water is discharged into streams and lakes, the excess dechlorinator has resulted in fish kills.I have seen it on lake Ontario. Therefore it is practice to control the amount of dechlorinator so there is no excess.

OP, you can grab a 02 test, and then add Prime to your water until you see the oxygen decrease. This will tell you the safe dose for your water. This is 'titration' and is a needed step to control how much dechlorinator is safe to add. But everyone's water will be different.

I did suffocate a bunch of goldfish 7 years ago but thought it was something else. I switched to Tetra AquaSafe and never had issues. 6 months ago I switched back over to Prime. Nothing has happened so far...

 

It's not the brand that matters, since they are all the same stuff.

Fish live on an amazingly small amount of dissolved oxygen, 8 ppm. If that small amount of oxygen gets cut in half down to 4 ppm the fish will start to suffocate and at 2 ppm will die. In a typical tank, this is a tiny amount of oxygen that the fish depend on. So only a small amount of chemical can cause a fish kill.

The problem is the rate at which the oxygen enters vs being taken out.

Adding a reducing chemical can cause the oxygen to be reduced immediately if there is nothing else to reduce like chlorine. Meanwhile, it takes 24 hours of aeration to bring the oxygen back. This is why we can get fish kills.

 

It's not the brand that matters, since they are all the same stuff.

Fish live on an amazingly small amount of dissolved oxygen, 8 ppm. If that small amount of oxygen gets cut in half down to 4 ppm the fish will start to suffocate and at 2 ppm will die. In a typical tank, this is a tiny amount of oxygen that the fish depend on. So only a small amount of chemical can cause a fish kill.

The problem is the rate at which the oxygen enters vs being taken out.

Adding a reducing chemical can cause the oxygen to be reduced immediately if there is nothing else to reduce like chlorine. Meanwhile, it takes 24 hours of aeration to bring the oxygen back. This is why we can get fish kills.

Huh...it happened to me with 3-4 goldfish, 3-4 fathead minnows in a 25G tub temporarily when the 75 cracked. I know it had at least 75G of filtration (it was an aqueon quietflow HOB.) I suppose it could've been a combination of temporary overstocking for 4 days + an overdose of Prime. This was 7 years ago and at the time, I thought "well, if Prime is the most used dechlorinator in the hobby and it detoxifies ammonia/nitrite, a bit of overdosing won't hurt." 30 mins to 4 hours later (can't remember exactly,) everyone started gasping for air; remember, these were GOLDFISH and MINNOWS - two fish species within the same family renowned for their ability to survive under extremely low oxygen concentrations.

So much has happened in the past 11 years. I can't remember it all

 

This is the same thing I see over and over actually. You describe the situation well.

Basically it goes like this:

- Fear of ammonia in tank, possibly new tank
- Add Prime cause it claims to detox ammonia. Add extra Prime.
- Fish suffocate


The sad thing is that Prime does nothing for ammonia.

 

This is the same thing I see over and over actually. You describe the situation well.

Basically it goes like this:

- Fear of ammonia in tank, possibly new tank
- Add Prime cause it claims to detox ammonia. Add extra Prime.
- Fish suffocate


The sad thing is that Prime does nothing for ammonia.

That's exactly what I thought too. It was only for a few days until I could get another 75 (actually got a 90 and an FX4 for free instead). I wasn't as knowledgeable about cycling as I am now, but I knew what ammonia/nitrite poisoning was and I didn't want my fish to suffer before the new tank was set up. Can't remember how much I dosed - maybe it was around 3× the amount? Then yeah, all that happened.

I was very hateful against Prime for the next 6-7 years and not only stayed away but cautioned others not to use it. I never knew it was the oxygen that killed the fish - I just assumed it was some sort of chemical reaction or toxicity. I was 12 years old then so...

But now I know, what exactly should I do? I got a small bottle of Prime a few months back and I'm using it. I haven't seen issues but didn't overdose either. Now I'm a bit apprehensive to use it some more. I kept my big ol' bottle of Tetra SafeStart. I know it works and it's not as cheap as Prime but is still an alright price.

I discovered API aqua essential which I presume is basically just rebranded Prime. I'll stay away. I know of Seachem Safe (concentrated, powdered Prime); It's cheap but if it's potentially dangerous for critters I don't want to risk it. I'm don't want a 5mL per 10 gal one; I much prefer a 5mL/50 like Prime. I have an old bottle of API Super Strength - not sure if it's still good but I can check. I have some donated Stress Zyme too.

I've heard many good things about Fritz and plan to try their products soon. Fritz Complete/Guard are dechlorinators. Do you recommend these?

Or should I just leave the water out for a day for the chlorine to evaporate off? I tested my source water many times and it's never had chlorine. Heck, I've almost forgotten to add dechlorinator many times (I never actually have though, but if I did I don't think anything would happen.)

Honestly, am I just overthinking it? Thousands, probably even millions, of fish folks use Prime. Hardly anyone has experienced issues. Mostly it's people who overdosed, are overstocked, or maybe a chemical reaction with their water. I'd checked my source water many times before - it's always showed 0ppm nitrite (once was .25 but that was during construction,) 0 ammonia, 10-20 nitrate, 6.8pH, 0 chlorine, 0 chloramines. I don't believe I've had the chance to check GH, KH, iron, phosphate, calcium etc, but when I do, I will.

Thanks for your input

 

Basically it goes like this:

- Fear of ammonia in tank, possibly new tank
- Add Prime cause it claims to detox ammonia. Add extra Prime.
- Fish suffocate

. . . instead of just doing a water change.

. . . Or should I just leave the water out for a day for the chlorine to evaporate off? I tested my source water many times and it's never had chlorine. Heck, I've almost forgotten to add dechlorinator many times (I never actually have though, but if I did I don't think anything would happen.)

Where does your source water come from? Do you get your water directly from a well, or does it come from a municipal or rural water system? If it's directly from a well, which is likely since testing shows no chlorine, there's almost certainly no reason to dose with Prime at all. I never do.

If you are on a water system then leaving the water out may not be adequate. While chlorine will evaporate off, some water systems treat their water with chloramine, and it won't.

 

Don't use any dechlorinator since you have no chlorine from your well. The brand does not matter since they are the same thing.

Test your source water for dissolved oxygen. If it is low (like 2-4 pm) then you can kill your fish if you use it directly and do a 100% water change with it.

I am on a well and also have low oxygen from the tap. So what I do is put the water in barrels and aerate it. In 24 hours the oxygen is up to 8 ppm and fish ready. Then I have a transfer pump to pump it into the tanks.


Adding Prime to non-chlorinated well water is bad. Since you don't have chlorine to reduce, the Prime may just reduce oxygen (depending on other things in the water). The more you add, the lower the oxygen goes. And on top of that, you are starting with low oxygen water anyway. So you may have 4 ppm Oxygen water to start with, add Prime, and reduce it to 2 ppm. All fish die.