Fish Nutrition – Short Bites

Jay Hemdal

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Fish Nutrition – Short Bites

Proper nutrition of captive fish is a very complicated subject. Virtually everything known about this topic is derived from fisheries science and therefore is related to growing fish for human food – where the fastest growth rate is most important. Long-term captive fish in aquariums have different needs. The following are some snippets of information regarding diets and feeding of aquarium fish, with the emphasis on giving information about the main issues, with the least amount of text.

Proper nutrition is vital to all animals. The fish in your aquarium rely solely on you to meet all of their dietary requirements, and their food must be provided in sufficient quantity to supply the energy they need in order to grow. The diet must also have the proper balance of fats, proteins, and carbohydrates, as well as the proper amount of vitamins and minerals.

On the other hand, too much food or food that is too high in calories will cause the fish to become obese. Not all fish have the same dietary requirements, and their needs even change as they grow. To top it off, over-feeding an aquarium can result in deteriorating water quality that will harm the fish.


Mixing medications with focus + food: This cannot work unless you calculate the dose properly. General Cure should not be dosed orally, as the two components have two different oral doses. This article discusses that: https://www.reef2reef.com/ams/proper-dosing-of-medicated-foods.780/

Using dietary supplements as a “medication”: The best diet in the world will not stop active infections – this is called the “chicken soup” syndrome. A proper diet is of course important for long-term fish health, it's just that changing to "great diet" will not stop any active fish diseases. Think of your pet dog – feeding it a great diet will do nothing to stop a flea or tick infestation if you take it for a walk in an infested field!

Adding vitamins or food additives to the aquarium’s water: Don’t do that. This just feeds the heterotrophic bacteria. Aquatic animals, if they uptake vitamins from the water at all, do so slower than the bacteria does.

True vitamin deficiencies: These are rare in fish. The two most common deficiencies are with Vitamin E and Thiamin (B1). These often need to be supplemented as they are not in great enough levels in many seafood items.

Food amounts: Some reef aquarists tend to underfeed their fish in order to try and limit nutrient and waste levels that would cause algae issues. This is not humane for the fish. Better to limit the number of fish in the reef tank instead. Some other aquarists may overfeed their fish. The one thing that they can do for their fish is to feed them, and some people take that to the extreme.

Fish not eating: Acute anorexia (where a fish suddenly stops feeding, or never starts feeding, and soon dies) is usually caused by some environmental issue; water quality problems, disease, transport stress or tankmate aggression. Chronic anorexia is a rarer problem, where the fish has apparently adapted well to captivity in all respects except that it does not show a normal feeding response. This can be due to the species’ natural history (only feeding on coral for example) or can sometimes be caused by collection with cyanide. Be sure to evaluate a non-feeding fish right away and take steps to resolve any environmental problems. Don’t fall into the trap of assuming the fish will begin feeding when it gets hungry enough, or conclude it must be eating something, just not when you are watching. A fish that does not actively pursue and consume food that you offer it is going to have problems surviving for the long term.

Fatty liver disease (Hepatic lipidosis): A major chronic health problem facing most long-term captive fishes is “fatty liver disease,” or liver degeneration. Fish do not assimilate fats well, so often, if a fish's diet is too high in fat, it will then be deposited in various tissues, especially the liver. Unlike with mammals, this fat is not readily usable during times of starvation. Even if food is withheld from a fat-laden fish, very little of the fat is ever reconverted into usable energy. Some fish do not show outward signs of obesity, especially sedentary species such as groupers and lionfish. In these, fatty liver disease may only be diagnosed after death, when sections of the liver will show oil droplets and pieces of the liver itself will float in seawater. With many animals, a period of acute anorexia can cause liver damage.

Fatty liver disease is most common in adult fish whose growth rate has slowed considerably. Younger fish tend to grow fast enough to minimize fat deposition—excess calories are turned into muscle tissue instead. With long-term captive fish, fatty liver disease is the leading cause of (or contributor to) death. Virtually every lionfish held in captivity longer than three years will show evidence of fatty liver disease upon necropsy.

Thiaminase: This is an enzyme that metabolizes or breaks down thiamine (vitamin B1). In high enough concentrations in food, thiaminase will create thiamin deficient diets in fish. This is a common, yet serious problem with predatory fish that are fed feeder goldfish, as goldfish are very high in thiaminase. Lionfish, piranha and oscars cichlids were commonly fed all-goldfish diets by home aquarists. Health issues in their fish were then very common; fatty liver disease in lionfish, pica in piranha (where they eat each other to try to get more thiamin). Fresh seafoods known to be high in thiaminase can be supplemented with thiamin. Conversely, aquarists can avoid feeding fresh seafoods known to be high in thiaminase.

The actual impact of thiaminase on a fish’s diet depends on three factors:
What proportion of thiaminase-containing food is fed to the fish
What the concentration of thiaminase is in the food item
How much vitamin B1 is already present in the food

Frozen foods: Food in the pet supply chain is not always handled very well. For decades, there have been issues with frozen fish foods being repeatedly thawed and refrozen while going from the manufacturing plant to your home. Each cycle degrades the product. It is really bad with brine shrimp...in that case, the subsequent refreezing causes large ice crystals that pierce the shrimp's body, allowing virtually all the nutrients to leak out.
 

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I have heard tell that primarily herbivorous and sponge eating fish that are not given algae and sponge based diets starve to death. The theory seems to be that they get constipated and stop eating. Do you have any thoughts/knowledge on this? Is it true?
 
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Jay Hemdal

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I have heard tell that primarily herbivorous and sponge eating fish that are not given algae and sponge based diets starve to death. The theory seems to be that they get constipated and stop eating. Do you have any thoughts/knowledge on this? Is it true?

Do you have some example species in mind? I've not had herbivores starve to death, even if fed mostly meaty seafoods. There are likely some delicate angelfish (Rock Beauties and some deep water Centropyge) that don't do well unless fed sponges, but I've not had issues in that regard because I steer clear of those.

I see a lot more constipation here on R2R, more than I ever see in my own fish. One possible cause is fish that gorge on Nori. Thinking back over the years, the only constipation I've seen was in fish that ingested foreign material, soft silicone for example. Back in the early 1980's we had an exhibit fabricator who made these really life like gorgonians by dipping knotted ropes in latex....killed a few angelfish before we got them removed from the tank!

Jay
 

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Foxface (and presumably other rabbit fish), moorish idol, regal angelfish, and potentially tangs. I hear about this from reefers in the UK where nori isn’t nearly as available. A famous one I follow has lost two foxes and a friend of mine on here can’t get his fox to a healthy weight like mine and the only difference is that I feed a lot of nori but he can’t often find it.


I’m just assuming herbivorous and sponge fed fish are healthier with more of that in their diet I guess?
 
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Jay Hemdal

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Foxface (and presumably other rabbit fish), moorish idol, regal angelfish, and potentially tangs. I hear about this from reefers in the UK where nori isn’t nearly as available. A famous one I follow has lost two foxes and a friend of mine on here can’t get his fox to a healthy weight like mine and the only difference is that I feed a lot of nori but he can’t often find it.


I’m just assuming herbivorous and sponge fed fish are healthier with more of that in their diet I guess?

Well, I can address the Moorish Idols - We have a pair of them since 2014 that have never eaten sponge or Nori while we've had them, they are doing great. In that same system, we have magnificent foxface and some really large spotted rabbitfish, same diet, no issues. We do feed some Mazuri gel diet though.

Jay
 

dennis romano

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Do you have some example species in mind? I've not had herbivores starve to death, even if fed mostly meaty seafoods. There are likely some delicate angelfish (Rock Beauties and some deep water Centropyge) that don't do well unless fed sponges, but I've not had issues in that regard because I steer clear of those.

I see a lot more constipation here on R2R, more than I ever see in my own fish. One possible cause is fish that gorge on Nori. Thinking back over the years, the only constipation I've seen was in fish that ingested foreign material, soft silicone for example. Back in the early 1980's we had an exhibit fabricator who made these really life like gorgonians by dipping knotted ropes in latex....killed a few angelfish before we got them removed from the tank!

Jay
I have owned two Rock Beauties. The first was about twenty years ago, the second, last year. In both cases, the fish was acquired at about two inches and in time grew to about four inches. Both fish had to be euthanized because they had gone blind. Twenty years ago, there wasn't any sponge food available. The recent fish ate sponge included food but still went blind. I still can't figure why the second lost its vision.
 

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Do you have some example species in mind? I've not had herbivores starve to death, even if fed mostly meaty seafoods. There are likely some delicate angelfish (Rock Beauties and some deep water Centropyge) that don't do well unless fed sponges, but I've not had issues in that regard because I steer clear of those.

I see a lot more constipation here on R2R, more than I ever see in my own fish. One possible cause is fish that gorge on Nori. Thinking back over the years, the only constipation I've seen was in fish that ingested foreign material, soft silicone for example. Back in the early 1980's we had an exhibit fabricator who made these really life like gorgonians by dipping knotted ropes in latex....killed a few angelfish before we got them removed from the tank!

Jay
Oh I just remembered where I first heard this. BRS claimed this with moorish idols. It’s discussed early in this video.

 
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Jay Hemdal

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I have owned two Rock Beauties. The first was about twenty years ago, the second, last year. In both cases, the fish was acquired at about two inches and in time grew to about four inches. Both fish had to be euthanized because they had gone blind. Twenty years ago, there wasn't any sponge food available. The recent fish ate sponge included food but still went blind. I still can't figure why the second lost its vision.

I had one rock beauty for four years and it literally didn't grow the whole time I had it. All the others I've ever had lived less than 6 months.

Jay
 

Debramb

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Jay, and other fish keepers, is variety in diet the best option?? I have tangs, Lemonpeel and Chromis, I try to give “high” end variety everyday. Probiotics pellets, seaweed extreme, ocean nutrition 2, nori etc. even the frozen are 4 or 5 different cubes, brine, mysis, emerald, etc. I thought they were at a good healthy weight until I saw absolutely awesome dive videos on YouTube that showed Sailfin, my length but much more filled out, same with Hippo. I think this is maybe more muscle mass? Better variety of course? Any suggestions for better diets? I’m concerned about fatty liver disease.
Thanks, Debra
 

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I like your article. 5 yrs in. I'm no expert but I've been feeding nori randomly. Chopped up clams from market, and some frozen ---> blood worms, krill, mysis. Don't seem to have an issue with diet. Maybe cause I give them different types everyday. Anyways, thanks for the read.
 

ISpeakForTheSeas

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is variety in diet the best option??
I can't answer all of the questions you've posed here (I'm curious about @Jay Hemdal 's suggestions for fatty liver prevention too), but I feel relatively confident answering this question.

Given that most aquaculture places use one, stable diet (using one feed and not switching feeds) for the broodstock of each species they work with and that fish need to be in basically peak physical condition to breed successfully, I'd say that a variety of feeds isn't always the best nutritionally.

One, good, quality feed is likely going to be better in a lot of situations.

That said, the best feeds for fish generally do have a good variety of ingredients (typically containing things like fish, crustaceans like shrimp or krill, bivalves, and different kinds of algae); the key is using ingredients that meet the various nutritional needs for most fish in the right quantities - as mentioned, some fish will need more/different kinds of meaty foods, some need more algae or a wider variety/different kind of algae, some may need sponges in their diet, etc., but in a reef tank setting with a wide range of fish, it's probably easier to feed a good quality "general/carnivore" fish feed and supplement it as needed for those fish with special dietary requirements (this is most commonly seen here when people feed frozen/pellets and supplement it with algae by offering nori to accommodate herbivores).

As a quick note here, not all ingredients (fish, crustaceans, bivalves, algae, etc.) are equally good - each species of fish, crustacean, bivalve, algae, etc. has its own nutritional profile/makeup; some fish will benefit more from some species than others (lion king discusses this in a few of their threads on predator nutrition here on R2R and Jay touched on this a bit above), but a few generalizations can be made (for example, salmon is almost always a good choice, same with clams of just about any kind, and with Ulva and Graciliaria and Halymenia macroalgae from what I've seen). The ingredients can also have a noticeable impact on the coloration of fish (which is why a lot of companies like to note that their feed contains astaxanthin and spirulina).

So, when considering feeds, as Jay said:
The diet must also have the proper balance of fats, proteins, and carbohydrates, as well as the proper amount of vitamins and minerals.
You want to consider the dry matter basis analysis for the protein, fat, etc. content of a feed (i.e. you want to look at how much protein, fat, etc. is in a feed once you get rid of the moisture in the feed - this is especially important for evaluating frozen feeds), and you want to consider the ingredients of the feed (too many grains and/or carbs is a no go - fish aren't designed to handle grains and carbs like humans do - and you want a good variety of ingredients to try and ensure that the feed contains the vitamins and minerals your fish need).

For what it's worth, my feed suggestions, my rationale behind those suggestions, and an explanation/discussion of dry matter basis can be found in the post linked below, but - basically - the best feed I've found on the market currently for hobbyists is LRS Reef Frenzy:
 

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People have been feeding GC soaked foods for decades.
 

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+1 for reef frenzy. I primarily feed that or fish frenzy (just depends on which the LFS has at the time).

I'm thinking of dropping the mysis and brine I supplement with and just going to frenzy at every feeding. Any reason I shouldn't?
 

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+1 for reef frenzy. I primarily feed that or fish frenzy (just depends on which the LFS has at the time).

I'm thinking of dropping the mysis and brine I supplement with and just going to frenzy at every feeding. Any reason I shouldn't?
Great diet with added fats and aminos
 

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I'm thinking of dropping the mysis and brine I supplement with and just going to frenzy at every feeding. Any reason I shouldn't?
Not really no.

I don't think that that supplementation would be bad by any means (it's a good mix of protein and fats, especially if algae loaded/mixed with algae like Spirulina Brine Shrimp), but, unless you want to offer variety for the sake of offering variety, I also personally don't see a reason to not feed frenzy at every feeding.
 

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Not really no.

I don't think that that supplementation would be bad by any means (it's a good mix of protein and fats, especially if algae loaded/mixed with algae like Spirulina Brine Shrimp), but, unless you want to offer variety for the sake of offering variety, I also personally don't see a reason to not feed frenzy at every feeding.
Well, that’s the (LRF), only one LFS carries it, locally I happened to be at Frank’s Tanks” in Fort Worth when Larry called for Franks order, I got to speak with him. He really does meet the fishing boat at the docks and immediately goes and processes it for flash freeze. This was a couple of years ago and I had just read that Hawaii’s institute had just successfully breed Yellow Tangs in captivity feeding LRF. Pretty cool. Personally I just like to cover more bases by variety.
 

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I try and add fresh human grade seafood occasionally. Too expensive to do it all the time but at least I know it’s fresh and has gone through a more vigorous control process. Currently that’s salmon and squid.
 

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Excellent thread!

I have 2 questions-

1. Fatty-liver is commonly associated sugar consumption as well - could it be due to the fact that a lot of dry fish foods are filled with wheat, flour, corn and other fillers?

Moreover, it seems natural that the size of an aquarium plays an important role in fish health - meaning a large fish with barely any swimming room will obviously have more health issues compared to the same fish in a much larger aquarium?

2. What other impact do grains, fillers, corn, etc. have on the long-term health of aquatic fish?


I was shocked at how many 'high-quality' fish foods contain large amounts of fillers and grains.
 
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