Instant Ocean Brown Residue

[X-37B]

So I switched back to IO regular after running ESV for over 5 years.
I ran 2 12 gallon batches in my brute and noticed the brown residue on the sides.
I just finished making 30 gallons for my remote fuge yesterday.
I put 1/4 cup of Rox carbon in a small nylon bag and floated it while mixing.
I have to run an air stone as I reduce the alk to 7.5.

The small amount of carbon picked up all the brown matter and the water was crystal clear with no residue on the sides of the brute.

Has anyone else tried this?

 

[blaxsun]

I haven't, but appreciate the tip.

 

[Randy Holmes-Farley Verified Community Expert]

I never got a brown residue with normal IO, only the tan precipitate of calcium carbonate. The brown reside from IO Reef Crystals may be vitamins, and that may be bound by GAC (although I wouldn't bother to do so).

What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com

Figure 1. The residue on the bottom of the plastic trash can that I use to mix Instant Ocean. I rarely clean it out. The solid is most likely calcium carbonate.

 

[austibella]

I clean out my brute can every time is make Saltwater I used instant ocean for years then I was getting more and more crud in my can, so I switched to Fritz pro RPM never had that problem again always mixes clean. Tropic Marin is also a good salt that mixes clean. BRS had a video on salts

 

[X-37B]

The brown film is really not an issue for me.
I only changed back because I can get 300+ gallons of IO regular for the price of 100 gallons of ESV.
I should have taken pics but it looks just like many of the brown film pics I have seen on threads.

 

[vtecintegra]

IO is nasty. I run an aquaclear power head with a filter while it's mixing. I still have to take paper towels and skim off what looks like brown dirt floating on the surface. I only keep using it because it's cheap and I like the alk level. Unrelated, but the last few purchases have been running low on calcium, down around 350~360, tested with two separate kits that agree. I'm having to dose calcium before use. This is what it does to my white container.

 

[X-37B]

IO is nasty. I run an aquaclear power head with a filter while it's mixing. I still have to take paper towels and skim off what looks like brown dirt floating on the surface. I only keep using it because it's cheap and I like the alk level. Unrelated, but the last few purchases have been running low on calcium, down around 350~360, tested with two separate kits that agree. I'm having to dose calcium before use. This is what it does to my white container.

Try a bag of carbon.
I get no brown residue at all running it.
I am only on my 1st bucket, have 2, and so far ca has been 420ish so not bad.

 

[Susan Edwards]

the brown residue is the anticaking agent they add

The 7 Best Reef Salt Mixes of 2026 – Reviewed And Tested

Mark has mixed and tested reef salt brands across his 125-gallon reef for years. Here's which mixes are batch-consistent, correctly balanced, and worth using in your system.

aquariumstoredepot.com

article lists which brands use anti caking agents. For my 65 gal container, no salt with the anti caking. impossible to clean that out. I did buy some IO for starting my set up and will use it for the awc or save as an emergency back up.

 

[Roli's Reef Ranch]

The only reason I can see to use reef crystals is because it SEEMS cheaper. BRS found that it mixes up to less than the labeled volume. On a per gallon basis, Red Sea Coral Pro came out to Almost exactly the same price when that’s factored in on a per gallon basis. Needless to say I’m no longer buying reef crystals, and not dealing with that kind of precipitation anymore.

 

[FourPawz]

The only reason I can see to use reef crystals is because it SEEMS cheaper. BRS found that it mixes up to less than the labeled volume. On a per gallon basis, Red Sea Coral Pro came out to Almost exactly the same price when that’s factored in on a per gallon basis. Needless to say I’m no longer buying reef crystals, and not dealing with that kind of precipitation anymore.

Is this based on MSRP? IO RC can be found for less than $40 regularly.

 

[vtecintegra]

That's what I was going to say. The cost comparison is BRS prices. IO on BRS is currently $50, and $38 on amazon. 24% cheaper.

 

[Roli's Reef Ranch]

Sorry, I miss-spoke, testing showed that Red Sea Coral Pro is actually less expensive! ‍

 

[austibella]

This is how i see it. We spend thousands and thousands of dollars on corals and fish and equipment. We won't blink an eye to spend a few hundred dollars on a new coral or fish. So why make water with all kinds of crap in it to save a few bucks? Cheeper is not always better .I changed to Fritz pro a while back it mixes clean and fast also I have used Tropic Martin again very clean I have used many other salts through the years and noticed mixing was getting dirtier and numbers were always off and I had to add more calcium, or magnesium and bring the PH up so for me I will spend the extra money, so i don't have to chase numbers trying to get my fresh saltwater parameters to where they should be. I do 70 gallon water changes every month. my corals and fish depend on me. So I give them the very best.but everyone's tank is different and needs different things so whatever works best for everyone is fine.

 

[Randy Holmes-Farley Verified Community Expert]

Sorry, I miss-spoke, testing showed that Red Sea Coral Pro is actually less expensive! ‍

Looks like my preferred mix (normal IO) is the cheapest of the bunch.

I'm not sure why anyone picks Reef Crystals over normal IO these days.

 

[Lost in the Sauce]

Sorry, I miss-spoke, testing showed that Red Sea Coral Pro is actually less expensive! ‍

Sure at $73/ bucket. I pay 39 at PetSmart.

With real numbers, the math doesn't work out to anywhere close.

 

[stephj03]

Sorry, I miss-spoke, testing showed that Red Sea Coral Pro is actually less expensive! ‍

Who in their right mind would pay $50-$60 for a 160g bucket of IO/RC when you can Amazon prime 200g worth for under $40?.

This chart gets referenced a lot and as such is a great marketing tool for BRS to sell the value of expensive salts, but it's not really connected to reality.

 

[stephj03]

It's all a wash on tanks under 100g where a bucket might last a yrs worth of water changes.

That's most reefers so I get it, similar price with or without residue.

On a big tank doubling your salt cost can make a difference IME.

 

[austibella]

the brown residue is the anticaking agent they add

The 7 Best Reef Salt Mixes of 2026 – Reviewed And Tested

Mark has mixed and tested reef salt brands across his 125-gallon reef for years. Here's which mixes are batch-consistent, correctly balanced, and worth using in your system.

aquariumstoredepot.com

article lists which brands use anti caking agents. For my 65 gal container, no salt with the anti caking. impossible to clean that out. I did buy some IO for starting my set up and will use it for the awc or save as an emergency back up.

Good article

 

[Mywifeisgunnakillme]

I never got a brown residue with normal IO, only the tan precipitate of calcium carbonate. The brown reside from IO Reef Crystals may be vitamins, and that may be bound by GAC (although I wouldn't bother to do so).

What is that Precipitate in My Reef Aquarium? by Randy Holmes-Farley - Reefkeeping.com

Figure 1. The residue on the bottom of the plastic trash can that I use to mix Instant Ocean. I rarely clean it out. The solid is most likely calcium carbonate.

Same here

 

[Miami Reef]

I use IO and it’s the best! I followed Randy’s advice and I went from annoying salt mixes that were expensive with brown crud and more metals, and too high Alk (instant ocean reef crystals, Red Sea coral pro) and I now use IO original. It’s the best! I haven’t ever had to clean my tub. It mixes extremely clean for me.