Aquatic v terrestrial

[RD.]

A fish that eats detritus in the wild does not do so because it is the best nutritional option available in their ecosystem, it does so because it has evolved over many years to survive on the waste of others. That has become it's niche, and it is about survival, not because it creates a nutritional advantage for the fish.

Terrestrial based plant matter has been shown to cause various issues in various species of finfish. It's not just a few plants, or just a few species of fish. It's numerous species, and if one considers some of the substances produced by these plants, it makes complete logical sense. As previously stated, the green pea, in a raw uncooked state, can carry high levels of phytic acid, tannins, and trypsin inhibitors (all are considered anti-nutritional matter) which can potentially cause negative health issues when fed in excess, to a fish.
No rocket science involved, or required, just some common sense.

This is not saying that some species of fish, in the wild, don't do just fine when consuming certain species of plants, seeds, nuts, fruit, etc, that over hundreds of years they have adapted to eat, and assimilate at least some of the nutrients found in that plant matter. But a glass box isn't the wild, and the OP was not feeding foods that fish typically consume in the wild.

Their digestive tracts are much longer compared to most other species, and this may allow for this adaptation.
Below an X-ray of pearsei.

Yes, absolutely, in the wild, but again in the wild they are not generally eating what hobbyists are tossing into their tanks, such as green peas. That, and many of the more herbivorous species of fish that have been studied over the years have demonstrated a great deal of plasticity when it comes to diet, and the length of their gastrointestinal systems.

For decades Tropheus keepers felt that due to the intestinal length & long digestive process in that species, it should only be fed low protein "green" food, and that any amount of animal based protein could cause bloat. Yet science has proven that in captive bred species of Tropheus the intestinal length can be half of what's found in wild specimens.

"Intestinal prolongation, although indicative of specialization on diets with low nutritional value, such as those of epilithic algae and detritus, has been shown to be highly plastic (Sturmbauer et al.1992). In Tropheus moorii the intestinal length of domestic fish measured only 50% of the length found in wild individuals (Sturmbauer et al. 1992)."

There have been other studies that have proven this with various other finfish species, it's a natural adaptation to the feast/famine conditions found in the wild.


So if we know that various species of fish can potentially have a negative reaction to some of the various anti-nutritional matter found in the more common forms of supermarket terrestrial based plant matter, and at the same time we have zero evidence to prove the same rule applies with aquatic based plant matter, why on earth fight common sense? Feed the fish what is generally accepted as safer over the long haul. Or continue to be stuck in outdated science from 50 years ago and feed green peas out of the can. Hmmmmm.

Would I be right in saying that the top quality "veggie" pellets/wafers have various types of kelp in them? I've often wondered about what effect, if any, a saltwater plant has on a freshwater fish. Is there no concern at all?

Not exactly. Kelp is much less costly compared to spirulina, so some commercial manufacturers went with kelp. Some use some of both, and some, such as the formula that I previously mentioned covered all of the nutritional basis, with a much wider mix. Below is the formula that I use to supplement "veggies" to all of the species that I keep, not just those with longer gastrointestinal systems. How much of that formula they recieve, depends on their classification.

 

[esoxlucius]

A fish that eats detritus in the wild does not do so because it is the best nutritional option available in their ecosystem, it does so because it has evolved over many years to survive on the waste of others. That has become it's niche, and it is about survival, not because it creates a nutritional advantage for the fish.

Terrestrial based plant matter has been shown to cause various issues in various species of finfish. It's not just a few plants, or just a few species of fish. It's numerous species, and if one considers some of the substances produced by these plants, it makes complete logical sense. As previously stated, the green pea, in a raw uncooked state, can carry high levels of phytic acid, tannins, and trypsin inhibitors (all are considered anti-nutritional matter) which can potentially cause negative health issues when fed in excess, to a fish.
No rocket science involved, or required, just some common sense.

This is not saying that some species of fish, in the wild, don't do just fine when consuming certain species of plants, seeds, nuts, fruit, etc, that over hundreds of years they have adapted to eat, and assimilate at least some of the nutrients found in that plant matter. But a glass box isn't the wild, and the OP was not feeding foods that fish typically consume in the wild.




Yes, absolutely, in the wild, but again in the wild they are not generally eating what hobbyists are tossing into their tanks, such as green peas. That, and many of the more herbivorous species of fish that have been studied over the years have demonstrated a great deal of plasticity when it comes to diet, and the length of their gastrointestinal systems.

For decades Tropheus keepers felt that due to the intestinal length & long digestive process in that species, it should only be fed low protein "green" food, and that any amount of animal based protein could cause bloat. Yet science has proven that in captive bred species of Tropheus the intestinal length can be half of what's found in wild specimens.

"Intestinal prolongation, although indicative of specialization on diets with low nutritional value, such as those of epilithic algae and detritus, has been shown to be highly plastic (Sturmbauer et al.1992). In Tropheus moorii the intestinal length of domestic fish measured only 50% of the length found in wild individuals (Sturmbauer et al. 1992)."

There have been other studies that have proven this with various other finfish species, it's a natural adaptation to the feast/famine conditions found in the wild.


So if we know that various species of fish can potentially have a negative reaction to some of the various anti-nutritional matter found in the more common forms of supermarket terrestrial based plant matter, and at the same time we have zero evidence to prove the same rule applies with aquatic based plant matter, why on earth fight common sense? Feed the fish what is generally accepted as safer over the long haul. Or continue to be stuck in outdated science from 50 years ago and feed green peas out of the can. Hmmmmm.





Not exactly. Kelp is much less costly compared to spirulina, so some commercial manufacturers went with kelp. Some use some of both, and some, such as the formula that I previously mentioned covered all of the nutritional basis, with a much wider mix. Below is the formula that I use to supplement "veggies" to all of the species that I keep, not just those with longer gastrointestinal systems. How much of that formula they recieve, depends on their classification.





View attachment 1410842

That ingredients list can only be described the dogs doodahs. As a comparison, and a piss poor one at that, my hikari algae wafers first mention of seaweed is six ingredients down the list and then it's only "seaweed meal". Spirulina is even further down the list! It's worth noting that all the first ingredients on the hikari list can only be described as those nasty fillers highlighted in a recent thread.

I went online to look at prices for NLS algae max and a 2kg tub of 2mm pellets is nearly £90.00 (uk), plus delivery! That is some coin for fish food.

 

[duanes]

I do not mean to poo the value of pellet food. I believe for most fish it is probably the best all round option.
In fact for most fish I used Algae Max, if I can get it (and if they will eat it).
But for certain species that have adapted to eating terrestrial plants, I don't believe pellets are my only option.

 

[RD.]

But for certain species that have adapted to eating terrestrial plants, I don't believe pellets are my only option.

I agree, but only if one is feeding those species of fish terrestrial based plants, that would be indigenous to their natural habitat. Or at least plants that would be similar in nutritional content. Which does not include plant matter such as uncooked green peas.

While processing removes most of the anti-nutritional concerns regarding terrestrial based plant matter, I still prefer to feed aquatic based plant matter, to aquatic based organisms. IMO AlgaeMax has been a game changer in this area of nutrition.

 

[DrownedFishonFire]

Believe the amazon during the rainy season depend on the fish and other wildlife as a vector to spread out the plant species. Especially during rain seasons. Plants and wildlife have evolved together. Including fish that has been there before the land animals we have evolved from the fish itself though. The pacus have developed jaw structure to crack nuts open. In Africa there are fish that feeds off the hippo fecal matter thats anything they eat. Fruits/vegs/aquatic plant/land plant matter. Everywhere across the globe we find examples of land plants being consumed by the fish driectly and indriectly. Remember we are the ones that evolved further than the fish. We have more complex digestive/nutritional needs than a fish though? Would i still feed my fish vegs yes. Fruits? No! Fruit to me is mainly glucose and fish dont get sugar nutrient out of it. Its for the land dwellers IMO. The veggies i feed might have fresh vitamins that cant be replicated in a lab setting or survive a drying process (thats my theory)

 

[DrownedFishonFire]

*It should not be a main feed. Just occasional supplement. I feed cucumber maybe twice a month for my fish. They are not known as specialized fruit/veg/nut eaters in the wild.

I do feed my fish frozen food in addition to their regular food maybe twice a week.

 

[RD.]

The veggies i feed might have fresh vitamins that cant be replicated in a lab setting or survive a drying process (thats my theory)

The reality is most vitamins found in raw ingredients survive processing, the rest can be added via a commercial vitamin premix, such as Polyphosphorylated L‐ascorbic Acid, a very stable form of vitamin c.
Polyphosphorylated L‐ascorbic Acid: A Stable Form of Vitamin C for Aquaculture Feeds


Nutrient Requirements of Fish (1993) is pretty much the bible on this subject, well worth a read for anyone interested. For most of the tropical species one has to extrapolate the info from commercial herbivores/omnivores/carnivores, to tropical species kept in the hobby, but most of that research is a valuable place to begin. Vitamins is not an issue, but that is not saying that certain enzymes and other nutrients are not lost along the way, once a raw ingredient is processed. Of course most of the tropical species of fish have never been studied long enough (if at all) for any real conclusions to be made one way or the other, as far as assimilation, digestible energy, bioavailability, etc.

But this was never a debate about feeding fresh/frozen, it was a debate regarding feeding terrestrial vs aquatic based plant matter. If you want to supplement your fish with plant matter, then my advice is do some research on the subject, and feed the appropriate plants - not vegetables from the supermarket. jjohnwm was on the right track. In the wild fish do not consume foods such as uncooked green peas, that are high in anti-nutritional matter, yet many hobbyists still feel that somehow they are a nutritional treat for their fish.

 

[jjohnwm]

This is a great thread; exactly what I come to MFK to read.

I'm not going to pretend to understand all the complexities of this debate, or of fish nutrition in general. I admit that before coming to this thread I had never even heard of the term "anti-nutritional" before; I had encountered the idea of such in reference to the effects of excessive consumption of rabbit by humans, which apparently results in malnutrition by interfering with the body's ability to absorb and metabolize certain elements of their food intake. It should have been intuitively obvious that similar problems could arise with other animals in general and fish in particular...but I never considered it.

RD, you seem to have a pretty good handle on this; what are your thoughts on the question of commercially available foods that claim to be "nutritionally complete" versus a diet of natural items that is as varied as possible in hopes of achieving the same end. I read here on MFK a lot of keepers suggesting that commercial pellets are the way to go; but half of those guys are talking about maintaining fish like Flowerheads or other unnatural creations that don't exist in nature and don't really have a natural diet. Same with reptiles; I once kept large numbers (of both individuals and species) of turtles, and commercial diets were sorely lacking. Today, there are pellets that claim to be perfect, and they have lots of proponents who claim they are. My gut says that even if I use these, I should supplement the diet with natural items like snails, fish, worms, etc...but if the pellets are truly complete, then feeding literally anything else is technically a step in the wrong direction.

What to do, what to do...?

 

[RD.]

RD, you seem to have a pretty good handle on this; what are your thoughts on the question of commercially available foods that claim to be "nutritionally complete" versus a diet of natural items that is as varied as possible in hopes of achieving the same end.

A quality pellet can be a nutritionally complete food, no doubt about it. Many long lived fish that have never ate anything but, including numerous species of fish that I have raised in captivity. Having said that, one can get the same job done feeding a diet of natural items that is as varied as possible. The only caveat being the latter will typically require some form of vitamin supplementation. It's hard to mimic mother nature in a glass box. Doable, but not always easy to achieve for the average hobbyist.

If one considers all of the various dietary specializations that take place in the wild, it's almost impossible to duplicate in ones home. When it comes to herbivores, especially algivores I prefer to cover a wide variety of aquatic based plant matter in the food as in the wild most freshwater as well as marine species tend to seek out and consume very specific types of plant matter, be it diatoms (Tropheus brichardi) green algae such as Cladophora (Tropheus moorii), or the filamentous green algae Mougeotia preferred by adult O. lidole in Lake Malawi. The fish in the Rift Lakes are no different than various marine fish that for whatever reason (nutrient content or availability) consume specific algae, some preferring red algae over brown, or green.


Feeding Electivity Indices in Surgeon Fish



The researchers in the study linked to above have been working on improving and/or fine tuning diets for captive Surgeon fish for the past 20 yrs or more. in 2001 they discovered that when the fish were fed greens alone (washed seaweed (ulva spp.), they suffered a high mortality rate, (approximately 80%), with the surviving fish showing clinical signs of malnourishment. Some had become emaciated to paper-thin condition.


While studying this genus in the wild they discovered that different species within this genus, preferred different forms of algae, some selecting several forms, while others chose green algae, over brown, or red.


Abstract

"Three species of surgeonfish A. canthurus coeruleus, A. bahianus, and A. chirurgus were captured in the waters of the Florida Keys (24°03'N, 81 °40'W). Items found in the stomachs of these fish were identified and analyzed for percent occurrence. These values were compared to percent occurrence values of the same items from random bottom transects taken at the point of capture to quantify any forage selectivity or avoidance behavior of these fish. A. bahianus selected for sand and chlorophytes and avoided phaeophytes. A. coeruleus also showed selection for sand and chlorophytes, while some A. chirurgus sampled selected for phaeophytes and others avoided them. A. coeruleus avoided sand and selected for rhodophytes, phaeophytes, and chlorophytes.


Introduction

Acanthurids are an important group of reef fishes, both because of the ecological impact of herbivores on reef ecology,2 and also because of their popularity as aquarium fish. The acanthurids are extremely abundant tropical and subtropical marine fish. Along with parrotfish (Scaridae) and damselfish (Pomacentridae), these animals are mostly herbivores, and together they form the largest part of the fish biomass of most reefs.5


Acanthurids are browsers, with lips and dentition for snipping off the tips and branches of algae. They also have long thin-walled digestive tracts and some species have a sand-filled, muscular gizzard-like stomach. These are all adaptations for foraging on relatively soft algal filaments and blades. Tangs, particularly when young, have a stringent requirement to feed almost continuously, undoubtedly because of a relatively poor utilization of their algal food.5 While the long, thin-walled intestine is probably well adapted to absorbing the contents of crushed algal cells; it may be poorly suited to handling cellulose. This has considerable bearing on their survival in model ecosystems, since they must have a food source that allows almost continuous foraging.1


The purpose of the reported study was to identify the natural foods of Atlantic acanthurids that have economic value to Florida's ornamental fish trade. This information is part of a larger study designed to define normal parameters for free-ranging acanthurids from Florida waters. The long-term goal of this work is to improve captive husbandry of acanthurids and other herbivorous reef species. This paper will describe surgeonfish feeding behavior in their natural habitat, and quantify their selectivity and avoidance of various forage items.



Materials and Methods

Fish and transect data were collected at several sites near Marathon Key, Florida (24°03'N, 81°40'W), on reefs using scuba gear. Once a suitable site was chosen, a diver would lay a 25 m transect line in a random direction and record all substrata and benthos (to the phylum level) along the line. The distance along the line that each phylum was present was also recorded. These data were later analyzed for percent occurrence.


A barrier net was deployed in a "C" shape for capturing the surgeonfish. A diver would locate a surgeonfish and attempt to corral it into the net, at which time the fish was collected with a hand net and transferred to a ventilated holding box on the bottom. Once ashore, captured fish were euthanized with buffered MS-222 (tricane methanesulfonate).


Stomach contents were analyzed for percent occurrence for each phylum present for each fish. Ivlev's electivity index4 for food selection was employed to quantify any selectivity or avoidance in the surgeon fishes' feeding behavior. The relationship is defined as E = (ri - pi) / (ri - pi), where E is the measure of electivity, r the relative abundance of prey item i in the gut (percent occurrence), and pi he percent occurrence of the same item along the transect measured on the bottom. The index has a possible range of 1 to - 1 , with 1 indicating active selection, zero indicating random selection or no consumption of the item, and-1 indicating avoidance of the item.4



Results

A. bahianus had the most (seven) phyla present in their stomachs. This species has a very muscular stomach with a relatively small lumen, which was always found full of sand. A. chirurgas also showed selection for sand. Its muscular stomach is similar to that of A. bahianus, and was similarly filled with sand, among which were a few bits of algae. Strong selection for chlorophytes was observed. A. coeruleus differ from the previously discussed species in that they have a thin-walled, relatively high volume stomach. These fish clearly avoided sand and strongly selected rhodophytes, phaeophytes and chlorophytes.


Discussion

Results of this study demonstrate that of three species of Atlantic surgeonfish studied, there were clear differences in natural diet and preference for different food items. The gross anatomy of the stomach and feeding habits of the A. chirurgas and the A. bahianus were similar, however the A. coeruleus was markedly different from the other species.

The stomachs of the ocean surgeonfish and doctor fish were grossly similar in that both species had a very muscular stomach with a relatively small lumen. These species both actively ingested calcareous sand, and the sand made up most of the material in the lumen of all samples taken. In addition to the ingestion of sand, the diet of these species was more varied than the blue tang, with foodstuffs from seven phyla being identified. One may speculate that they gather essential nutrients from these organisms that are absent in a strictly vegetarian diet. Alternately, it may be that these items have been incidentally eaten while browsing on algae, and not selected for at all. These items, which may be missing from commercially available diets, may be important for optimal health of captive acanthurids.


In contrast, the stomach volume of the blue tang was comparatively large, and the structure was characterized as thin-walled and tubular. The blue tangs actively avoided ingestion of sand. These animals had a demonstrated preference for red algae, which was surprising as it is considered to have a lower nutritional value than other algal groups. 3 It is possible that by seeking out rhodophytes they are trying to meet some unknown nutritional requirement.


These findings may eventually for captive acanthurids be applied to the improvement of husbandry programs and diets."



Acknowledgements



The authors wish to thank: Florida Sea Grant, Roy Hemdon, John Than, Charles "Chuck" Cichra, Chris and Jane Bowen, and Brian Bowen.



References



1. Adey, H. and L. Loveland. 1991. Dynamic Aquaria. Building Living Ecosystems. Academic Press, San Diego, Pp. 643.



2. Carpenter, R.C. 1986. Partitioning herbivory and its effects on coral reef algal communities. Ecological Monographs 56"343-363.



3. Montgomery, W.L. and S.D. Gerking. 1980. Marine macroalgae as foods for fishes: an evaluation of potential food quality. Environmental Biology of Fishes 5:143-153.



4. Strauss, R.E. 1979. Reliability estimates for Ivlev's electivity index, the forage ratio, and a proposed linear index of food selection. Transactions of the American Fisheries Society 108:344-352.



5. Thresher, R. 1980. Behavior and ecology on the reef and in the aquariums. Palmetto Publishing, St. Petersburg, FL, Pp. 171.

..................................




So if the goal is to mimic nature, we first need to know what that fish is primarily consuming in the wild, and then one needs to mimic that as closely as possible. Clearly feeding green peas, spinach, broccoli and the like may not be as natural, or nutritional, as some may think.

I will also add, that keeping the marine species above, healthy long term, is not difficult to do if you can get them on a high quality pellet food.


30 or 40 yrs ago this would have been impossible to achieve in captivty, no matter what you fed.

Moorish Idol Extravaganza!

Moorish Idol 500 gallon tank, all the Moorish Idols have been in this tank for 4+ years, no losses. Not something that one sees everyday, or for that matter - ever! Just thought that I would share.

www.monsterfishkeepers.com

 

[jjohnwm]

It's been shown that some species of birds develop much longer intestines during the winter months, allowing them to more efficiently use plant matter/seeds for food. During the summer months they switch to a diet of insects and the intestines shrink considerably, only to re-lengthen in the autumn. The Yellow-rumped Warbler is one of the most common North American warblers, and it displays this adaptation. It is thus one of the earliest warblers species to arrive in the spring (showing up well before any significant amounts of insects are available) which is thought to give it an advantage over it's tardier relatives. It also tends to hang around a bit later into the fall, sometimes even overwintering in milder climates...something other species just can't manage.

I wonder if the fish that show shorter digestive tracts in captivity are "fixed" in this respect throughout their lives, with each successive captive-bred generation having progressively shorter intestines, or if individual fish experience a shortening of the gut throughout their lives. Would this extend to the possibility of the gut re-lengthening if the fish were re-introduced to a completely natural diet again?

It would be interesting to experiment with tank-bred individuals by introducing them to a large enough outdoor pond that a natural growth of algae/aufwuchs/whatever could sustain them. All it would take is vast quantities of time, money and space....and, of course, an environment that isn't encased in ice for over half of each year...