Frozen vs. Pellet Foods

[BeanAnimal]

I avoid Reef Roids...makes my phosphate go crazy for some reason

Way back when my tank was kind of new, not as far back as when @Paul B was taking a wagon to school, but before @revhtree said "hey I want to start a fish forum"....

I used Reef Roids at the recommendation of a club member. A lot of Reef Roids.

I can trace the beginning if my insanely high phosphate back to that point. You observation may have merit, but I am not sure that anybody has actually tested to see what the actual concentration is.

I can only assume that because it is a fine powder that it settles everywhere and breaks down quickly into orthophosphate before being directly consumed by coral or other macro organisms.

 

[Australian_Reef]

Way back when my tank was kind of new, not as far back as when @Paul B was taking a wagon to school, but before @revhtree said "hey I want to start a fish forum"....

I used Reef Roids at the recommendation of a club member. A lot of Reef Roids.

I can trace the beginning if my insanely high phosphate back to that point. You observation may have merit, but I am not sure that anybody has actually tested to see what the actual concentration is.

I can only assume that because it is a fine powder that it settles everywhere and breaks down quickly into orthophosphate before being directly consumed by coral or other macro organisms.

It’s basically powdered phosphate.. the corals love it. Then we are left with the remainder. Roids is a good description

 

[Paul B]

@Paul B have you seen the Australian aquarist on YouTube?

No, I never heard of him, but I also never heard of Bean Animal.

I did start my SCUBA diving career in Sydney Australia in 1971 and I loved it.
A girl I met there named Christine took me on a very nice yacht and I have been diving ever since.

 

[strich]

I find my tangs do best on romaine lettuce.

Isn't lettuce technically just not very good for them?

 

[Australian_Reef]

No, I never heard of him, but I also never heard of Bean Animal.

I did start my SCUBA diving career in Sydney Australia in 1971 and I loved it.
A girl I met there named Christine took me on a very nice yacht and I have been diving ever since.

Ah well maybe you check out that channel on Christine’s sake?

 

[Australian_Reef]

Isn't lettuce technically just not very good for them?

Yeah it’s awful. But the way this thread is going….

 

[keagan]

Isn't lettuce technically just not very good for them?

It's not very good for us it's almost all water small amounts of vitamin a and potassium but it's like 94% water on the low end. Iceberg lettuce is the worst though. Macro like nori or dulse have alot more nutrition.

 

[Grog]

It’s basically powdered phosphate.. the corals love it. Then we are left with the remainder. Roids is a good description

I can trace the beginning if my insanely high phosphate back to that point. You observation may have merit, but I am not sure that anybody has actually tested to see what the actual concentration is.

I feed Reef Roids about once a month. Less lately because, well I forgot.

This conversation made me look back at when I was feeding the Reef Roids regularly vs. not and I have to agree with the above. There was definitely a link between when I was feeding the Roids and my PO4 tests having high results.

Maybe I should reconsider this behavior.

 

[strich]

Yeah it’s awful. But the way this thread is going….

Hah. Yeah look I don't mean it's evil or anything. But when I first started looking into this hobby it was presented as kind of a normal part of the diet, but in fact it's kind of pointless as it provides no nutritional value. I did find it initially a bit misleading.

 

[vlangel]

I feed frozen every day mixing up between mysis, prime reef, marine cuisine, emerald entree, spiralina enriched brine shrimp and seaweed delight. I also use an auto feeder to dispense flakes and pellets once a day every day. That has helped me keep my fish in good health so they can live long lives, some for 10-15+ years. I also feed nori, and lettuce or kale from my garden for the herbivores and some live food when I can get it.

 

[Paul B]

Ah well maybe you check out that channel on Christine’s sake?

Christine is 80 now, I doubt I would recognize her.

 

[Freenow54]

Way back when my tank was kind of new, not as far back as when @Paul B was taking a wagon to school, but before @revhtree said "hey I want to start a fish forum"....

I used Reef Roids at the recommendation of a club member. A lot of Reef Roids.

I can trace the beginning if my insanely high phosphate back to that point. You observation may have merit, but I am not sure that anybody has actually tested to see what the actual concentration is.

I can only assume that because it is a fine powder that it settles everywhere and breaks down quickly into orthophosphate before being directly consumed by coral or other macro organisms.

My son was nuts about them. We ended up with the best Hair Algae crop in the Continent

 

[Australian_Reef]

Hah. Yeah look I don't mean it's evil or anything. But when I first started looking into this hobby it was presented as kind of a normal part of the diet, but in fact it's kind of pointless as it provides no nutritional value. I did find it initially a bit misleading.

Yes I was joking .. I probably did feed it 20 years ago though.

 

[Paul B]

Some scientific links to gut bacteria and how it works on the immune system:

In my opinion dry foods contain no beneficial microbes and do nothing for immunity. "it's just me"

The Main Event – Bacteria In The Digestive System​

The human gut is home to a huge range of microorganisms, most of whom enjoy the ideal temperature, acidity level and nutrient supply of the human body. The benefits of bacteria in our digestive system are incredibly important. Without them, we would be unable to digest our food, synthesize certain essential vitamins, absorb water, and fend off the dangerous bacteria that often tries to attack our gut. Some of the most important good gut bacteria include Lactobacillus, Bifidobacterium, Akkermansia muciniphila and Faecalibacterium prausnitzii. In the stomach and digestive tracts, the most populous pathogenic bacteria include Salmonella, Clostridium, and E. coli. Food poisoning is probably the most common symptom of a bad gut bacteria taking control, but if you have enough beneficial bacteria in your stomach, you should be able to recover quickly.

Good vs. Bad Bacteria (Photo Credit: chombosan / Fotolia)​

As mentioned earlier, a significant amount of the immune system also operates out of the gut, making it one of the control centers for our overall health. Keeping the balance between “good” and “bad” microflora in this part of the body is especially important. The beneficial bacteria found in the digestive system are called probiotic bacteria, and there are also a number of foods that contain probiotics to improve your bacterial balance. If you increase the amount of probiotics in your diet (and gut), you can neutralize harmful bacteria and reduce symptoms of diarrhea, inflammation, nutrient deficiency, cramps, constipation and bloating, as well as more serious stomach conditions and diseases.

So… What’s The Problem?​

As mentioned at the top of the article, in the past few decades, we have become an increasingly “sterilized” society. For example, antibiotics can destroy both good and bad bacteria, ultimately weakening our immune system and making pathogenic bacteria more adaptive and difficult to cure. It has become quite common for parents and doctors alike to turn to antibiotics, as they are inexpensive and proven methods to treat infections, but that doesn’t mean it’s a good thing in the long run. Our hand sanitizers and intensely hygienic modern world has made it harder to have a diverse and balanced gut ecosystem.
Additionally, our diet has a significant impact on the bacteria in our bodies, but a diet high in artificial sugars, excess starches and vegetable oil can harm that balance. As more and more processed foods enter our cultural habits, the more susceptible we are to infection and poor health. Combine that with harsh, chemical cleaning products and heightened stress levels.
Furthermore, our bodies develop tolerances and antibodies based on the bacteria that we are exposed to, largely in our early years. Research has shown that children playing in the mud, eating dirt and generally exposing their immune systems to a wide range of bacteria actually helps them have a stronger immune system as they age.
"One reason I add mud to my tank, by Me"
Modern cleanliness and germ-obsessed behavior has robbed the past generation of those bacteria base-building experiences.
"Sounds like some quarantine tanks to me. by Me"
At the end of the day, if you want to protect the health and wellness of your whole body, you should start with the stomach. Keeping that balance in the eternal battle between “good” and “bad” bacteria is a lifelong journey, but one that is extremely important!

1. 
   https://www.reef2reef.com/javascript:void(0)

Gut bacteria are essential regulators of the immune system, shaping immune cell development, maintaining barrier integrity, and balancing inflammatory responses.​

Gut Microbiome and Immune Interaction​

The human gut hosts trillions of microorganisms, collectively known as the gut microbiome, which interact closely with the immune system. The Gut-Associated Lymphoid Tissue (GALT), containing over 70% of the body’s immune cells, continuously monitors the gut environment, distinguishing between harmless microbes and potential pathogens scienceinsights.org+1. This constant interaction ensures the immune system remains alert yet tolerant, preventing overreactions to beneficial bacteria or dietary components.

Gut Bacteria Strengthen The Physical Barriers In The Gut​

The inner walls of the gut are lined with slimy mucus secreted by cells in the intestinal epithelium. This stops the microbes from attaching to the inner surface of the gut and breaching our body. This mucus also contains proteins capable of harming bacteria, such as Muc2.

However, mucus can’t always stop bacteria from attaching to the gut, as bacteria have certain adherence factors that help them stick to the inner gut’s surface.



Once attached to the gut lining, the bacteria’s presence stimulates the intestinal epithelial cells to produce more mucus. As the mucus thickness and quantity increases, it makes it increasingly difficult for pathogenic bacteria to attach themselves to the inner gut surface.

The mucus layer prevents bad bacteria from forming clusters in the gut. (Photo Credit : Creative Commons)


In many ways, this is a first-come, first-serve situation; good gut bacteria attach themselves to the gut and then make life difficult for any other bacterial species that is trying to gain a foothold and survive.

 

[Paul B]

Here is a long, scientific one about gut microbiome in fish:

https://www.frontiersin.org/journal...logy/articles/10.3389/fcimb.2025.1639426/full

 

[strich]

That's a rather large copy pasta there Paul. I don't think anyone disagrees with the science around humans. But there is a lot more devil in the details it seems with closed system marine tanks, and I think some of your opinions have maybe accidentally gone a bit beyond what the science suggests.

I've enjoyed reading both yours and Randy's thoughts so far, and thought I'd add a few papers I found and at least read and understood the abstracts for. Note that the below are AI-assisted so you should definitely validate the summary against the paper itself if you doubt it.

• Jang et al. (2022) showed that while fresh/raw feeds drove faster physical growth in flounder, they also increased opportunistic gut pathogens, whereas extruded pellets yielded a cleaner, probiotic-leaning microbial profile.
• Luo et al. (2024) found that while live/raw foods cause an initial surge in gut microbial diversity, the fish's intrinsic physiology stabilizes its gut microbiome back toward a core baseline over time. Plus, in an established closed reef system, fish fed a pellet-only diet still regularly ingest benthic microfauna, algae, and rockwork biofilms, which continuously inoculate their gut with beneficial ambient bacteria anyway.
• Gu et al. (2024) demonstrated that fresh marine meat drastically outperformed standard commercial pellets in short-chain fatty acid (SCFA) production, which directly stimulates gut-associated lymphoid tissue (GALT). Though a custom pellet with 40% high-grade fishmeal closed almost the entire gap, proving the issue is cheap plant binders rather than the pellet form factor itself.
• Rai et al. (2025) explains the underlying mechanism: gut microbes act as a "second genome" by fermenting unrefined dietary substrates into SCFAs that prime mucosal IgT antibodies, meaning unrefined whole foods do genuinely offer superior mucosal immune stimulation compared to heavily processed, starch-heavy dry feeds.

So, my read of this is that pellets don't do nothing, and fresh foods aren't a magic bullet. High-heat commercial pellets can lack the unrefined substrates needed for maximum SCFA-driven gut immunity, while raw/fresh foods drive better growth and mucosal priming at the cost of carrying higher ambient bacterial loads. An established closed system seems to eventually provide the fish with a baseline gut bacteria as they feed on various parts of the tank, no matter the feed type.
The science heavily points toward a hybrid approach: feed quality pellets for baseline nutrient stability and convenience, and supplement with raw, whole marine seafoods (mysis, whole squid, bivalves, nori) to maximize gut microbial diversity and immune response.

 

[Paul B]

Very interesting.

 

[keagan]

That's a rather large copy pasta there Paul. I don't think anyone disagrees with the science around humans. But there is a lot more devil in the details it seems with closed system marine tanks, and I think some of your opinions have maybe accidentally gone a bit beyond what the science suggests.

I've enjoyed reading both yours and Randy's thoughts so far, and thought I'd add a few papers I found and at least read and understood the abstracts for. Note that the below are AI-assisted so you should definitely validate the summary against the paper itself if you doubt it.

• Jang et al. (2022) showed that while fresh/raw feeds drove faster physical growth in flounder, they also increased opportunistic gut pathogens, whereas extruded pellets yielded a cleaner, probiotic-leaning microbial profile.
• Luo et al. (2024) found that while live/raw foods cause an initial surge in gut microbial diversity, the fish's intrinsic physiology stabilizes its gut microbiome back toward a core baseline over time. Plus, in an established closed reef system, fish fed a pellet-only diet still regularly ingest benthic microfauna, algae, and rockwork biofilms, which continuously inoculate their gut with beneficial ambient bacteria anyway.
• Gu et al. (2024) demonstrated that fresh marine meat drastically outperformed standard commercial pellets in short-chain fatty acid (SCFA) production, which directly stimulates gut-associated lymphoid tissue (GALT). Though a custom pellet with 40% high-grade fishmeal closed almost the entire gap, proving the issue is cheap plant binders rather than the pellet form factor itself.
• Rai et al. (2025) explains the underlying mechanism: gut microbes act as a "second genome" by fermenting unrefined dietary substrates into SCFAs that prime mucosal IgT antibodies, meaning unrefined whole foods do genuinely offer superior mucosal immune stimulation compared to heavily processed, starch-heavy dry feeds.

So, my read of this is that pellets don't do nothing, and fresh foods aren't a magic bullet. High-heat commercial pellets can lack the unrefined substrates needed for maximum SCFA-driven gut immunity, while raw/fresh foods drive better growth and mucosal priming at the cost of carrying higher ambient bacterial loads. An established closed system seems to eventually provide the fish with a baseline gut bacteria as they feed on various parts of the tank, no matter the feed type.
The science heavily points toward a hybrid approach: feed quality pellets for baseline nutrient stability and convenience, and supplement with raw, whole marine seafoods (mysis, whole squid, bivalves, nori) to maximize gut microbial diversity and immune response.

My theory is if some day we decrease microbial diversity by replacing most species with an inoculated species it might help with post introduction survival of wild caught fish by out competing pathogens, and possibly also increasing bioavailability of nutrients in the dry food.

I'm curious to see what having one dominant species of gut bacteria does. They had lactobacillus become the dominant species in the microbiome of salmon in study years ago but haven't proved the same positive effects as it has in humans.

"Lactobacillus Dominate in the Intestine of Atlantic Salmon Fed Dietary Probiotics - PMC" https://pmc.ncbi.nlm.nih.gov/articles/PMC6343587/

If it outcompetes opportunistic pathogens or helps digestive function it could have some implications to the hobby. Having evidence that says probiotics added to dry food are a positive to some fish species would be useful.

For now the evidence really is lacking to say conclusively one is better but like you said it does illustrate how a hybrid approach may have merit.

 

[DragonWrasseFan]

I personally would not feed any dry foods to anything except worms.

Dry foods won't have the essential oils of natural foods, are full of fillers like flour that offer no nutrition and have no living gut bacteria that controls immunity almost 100%.

Just my opinion, but in over 45 years none of my fish have ever been medicated, quarantined or died of any communicable disease and some of them are over 35 years old.

Of course, dry foods won't kill them, it's just not as good and most fish never get dry foods on the reef where they come from.

This makes me rethink my feeding strategy. I feed frozen in the morning and evening, also sometimes I feed more frozen in the middle of the day if the fish look extra hungry. I also feed either flake or pellets in the morning with the frozen. I love feeding a variety of frozen the most though so maybe I’ll just stick with that. EDIT: also my fish tend to go more crazy for frozen.

 

[strich]

This makes me rethink my feeding strategy. I feed frozen in the morning and evening, also sometimes I feed more frozen in the middle of the day if the fish look extra hungry. I also feed either flake or pellets in the morning with the frozen. I love feeding a variety of frozen the most though so maybe I’ll just stick with that. EDIT: also my fish tend to go more crazy for frozen.

The thing that Paul didn't get quite right in that particular post though is that quality dry food can offer a more balanced and varied diet overall even if it does miss a few important components. The science so far suggests you should be feeding both dry and fresh. More variety is better.