Why fewer fish in reeftanks than in freshwater?

[Mihai]

Sorry if it's a stupid question but I understand that it's common knowledge that in reef tanks we have to keep fewer fish for the same volume of water than in a freshwater planted tank. Why?

I can bring arguments to the opposite: in the reeftank I have a whole bunch of recyclers (snails, worms, sponges, algae scrubbers, etc.) while in a planted freshwater we only have the plants (if at all). In terms of filtration, for marine you have the skimmer that does a great job, you have the live rock...

So... why?
Thanks,
Mihai

 

[melas]

i'm sure there are other reasons but i think a large part of this ideology is due the scale of each of the environments. Freshwater fish are often found in only a few inches of water with highly variable water quality set off by precipitation and runoff. marine environments are of a much larger scale and far more stable in their water quality. reefs are teaming with life but the density of fish per gallon is far lower than that of a tropical stream or an african lake.

 

[fishfanatic2]

IIRC a container of saltwater will also contain less oxygen than a container of freshwater of the same volume.

 

[FragMaster]

The main reason's are metabolisms, and bio waste.
In the marine enviorment a fish 's metabolism is MUCH faster then a fish in freshwater. This means they grow faster, eat more, and produce MUCH more bio-waste and produce a MUCH larger bio-load on the system then that of a fresh water fish.
Not to mention another side effect of a high metabolic fish is over feading.
SImply, the less fish in a reef the better, unles you have a large tank, Large filtration system, and enough living substraight to counter the waste that all your snails, crabs make too. THat salso a fact that is often over looked. Crabs and snails poop too! LOL!

 

[Anonymous]

Freshwater fish and plants will live happily in a sewer that would leave your nice sps frags as white as snow.

 

[Mihai]

Why would fish in marine tanks have faster metabolism?

Also, I'm sure that they are some delicate freshwater fishes (discus, angels, etc) that would not thrive in a sewer...

Also, many marine fish live in shallow water (I know much deeper lakes).

Regarding the oxigen - I'm running a skimmer and an algae scrubber on reverse cycle, so it's not an issue...

M.

 

[melas]

my reply was not referring to depth as much as volume . . . fish per gallon. . . space. . .these are the things that stress marine fish, lowering immuno responses. . . you skim all you want. . . . . .once you pass the point of saturation there is nothing you can do to dissolve more oxygen in water other than decreasing temperature, decreasing salinity, or increasing pressure. the saturation level of saline water is much lower than that of fresh water. basically you can not sustain the same level of respiration in marine envrionments as in fresh.

 

[Anonymous]

It's the chemistry of saltwater. pH: At the lower pH of freshwater, ammonia (NH3) mostly converts to ammonium (NH4+), which is pretty much harmless. So you can cram a whole bunch more fish in the same space. Dissolved oxygen: The amount of dissolved O2 is likely (I'm assuming) a limiting factor in the number of nitrifying bacteria a given volume can support, and thus the amount of waste a given volume of water can safely mineralize. Saltwater can't hold nearly as much oxygen as freshwater, regardless of how much you aerate/skim.

I have never heard that SW fish have a higher metabolism than FW fish, or grow any faster. Any links to back this up?

 

[Len]

Also, I'm sure that they are some delicate freshwater fishes (discus, angels, etc) that would not thrive in a sewer...

I guess sewage is a relative term. Amazon's waters (where discus and angels come from) are extremely nutrient rich. There's an incredible amount of dissolved organics in the water.

 

[FragMaster]

Not only the salt increases there metabolic rate , but also the water temperature versus most fresh water temperatures.
Higher temps year round equal more active fish, equals a higher metabolic rate.

The salt and the temperature of the water they live in.
SInce you mentioned low oxygen levels, that plays a HUGE role in ther faster metabolic rate.
Since saltwater has lower oxygen levels available for them to take in thier gills work harder to take more water in. The harder a fish works to breath the faster its metabolism becomes.
Its called areobic metabolism
Do a google search for aerobic metabolism.
This link pertains to low oxygen in general and not only to salt water fish , but it stands to reason its true.
http://oxyedge-chum.com/oxygen_or_salt.htm

The reason fresh water fish grow relativly slower and smaller than marine fish is that they do not need to eat as much to survive, very few of them have the same metabolism as a saltwer fish.

The lower the availible oxygen levels the faster the metabolic rate, the fatsert the metabolic rate means more energy used, more energy used means more food must be consumed more often. AND since most marine foods are MUCH higher in protiens and nutrients It provides an excellent situation for massive growth.
(of course I am not talking about all marine fish growing larger than freshwater, that would be silly. Im speaking in general terms.

 

[Anonymous]

Not only the salt increases there metabolic rate

Huh? Where are you getting this from? Where have you read or seen that salt increases the metabolic rate of fish?

but also the water temperature versus most fresh water temperatures.
Higher temps year round equal more active fish, equals a higher metabolic rate.

Most people keep their FW tanks at the same temperature as SW tanks; in the wild tropical regions where fish are coming from are very near the same temperature regardless of FW or SW.

The salt and the temperature of the water they live in.
SInce you mentioned low oxygen levels, that plays a HUGE role in ther faster metabolic rate.
Since saltwater has lower oxygen levels available for them to take in thier gills work harder to take more water in. The harder a fish works to breath the faster its metabolism becomes.

Animals in low oxygen environments usually have lower metabolism. I do mean a permanent environmental lower oxygen level, such as at the bottom of a still lake, or the bottom of the ocean, or a stagnant pond, not the temporary low blood oxygen level that occurs after a fish has become stressed, or fought, or has been swimming around a lot. Two entirely different things.

Its called areobic metabolism
Do a google search for aerobic metabolism.
This link pertains to low oxygen in general and not only to salt water fish , but it stands to reason its true.
http://oxyedge-chum.com/oxygen_or_salt.htm

It refers to low oxygen in the blood after a fish has fought on a line. Clearly if you chase a fish around its metabolism will increase, and the dissolved oxygen in its blood will decrease. This doesn't mean a lower oxygen level equals a faster metabolism! Can you find a link that discusses the differences in metabolism between FW and SW fish? I can't.

The reason fresh water fish grow relativly slower and smaller than marine fish is that they do not need to eat as much to survive, very few of them have the same metabolism as a saltwer fish.

Again, do you have a source for this type of info? I have never heard that marine fish grow slower than freshwater fish.

The lower the availible oxygen levels the faster the metabolic rate, the fatsert the metabolic rate means more energy used, more energy used means more food must be consumed more often. AND since most marine foods are MUCH higher in protiens and nutrients It provides an excellent situation for massive growth.
(of course I am not talking about all marine fish growing larger than freshwater, that would be silly. Im speaking in general terms.

See above. I've never heard of the things you're stating.

 

[FragMaster]

WHy the attack?

Post a link that states the oposite and I will post one that states it is so.


http://facstaff.morehouse.edu/~lblumer/ ... d%20MR.pdf
Read the introduction and then the second page.
It is based on mollies though and the only thing I can readily find on it.
I will keep searching.
The introduction describes what one would "think" would happen, the second describes what did happen.

I could also be interpeting this thing entirely wrong, but thats what I have alsways been told.

Here is another on brackish water fish, Man finding my proof is harder than I thought. BUT I WILL DANG IT!!! LOL!
http://www.masla.com/brackish.html

"Marine fish


The loss of water to the external environment is a problem that all marine fish must deal with. The marine environment in which the fish lives is hyperosmotic to the internal environment, i.e. there is a higher salt concentration in the water than inside the cells. This results in an osmotic gradient in which water is lost from the fish to the environment while ions are gained by diffusion. Ions are excreted by specialised glands.


Freshwater fish


The freshwater environment is hypo-osmotic to the internal environment of fish, i.e. there is a lower salt concentration in the water than inside the cells. This results in an osmotic gradient in which water is gained by the fish from the environment without drinking and salts are lost by diffusion. Ions are absorbed in the gut and by active uptake across the gills. "

Found here: http://hsc.csu.edu.au/biology/core/bala ... .html#net4

TO me That means more energy spent which means higher metabolic rate.

Here's another.
http://www.publish.csiro.au/paper/MF98130.htm
Now whatch and see I have probably just hung my self with my own links by not understanding scientific terms! LOL!!!

http://groups.msn.com/Breedingtropicalf ... ation.msnw

 

[Mihai]

OK, so in the end is pH <-> ammonia and oxygen? Also, maybe the worry of having high DOM?

I guess that they can be taken care by a huge fuge with macroalgae (plant life) .

M.

 

[FragMaster]

Yup the more water volume the better.

 

[Anonymous]

WHy the attack?

Sorry, I don't mean this to sound at all like an attack. I am asking honest questions here that I don't know the answers to myself. I am not saying the opposite of what you are saying is true. Just skeptical of what you are stating.

Post a link that states the oposite and I will post one that states it is so.

I tried finding a link that says FW and SW fishes have about the same metabolism, but no luck. I think the burden of proof lies with you on this one.

http://facstaff.morehouse.edu/~lblumer/BIO_320L/Salinity%20and%20MR.pdf

This is in regards to changes in salinity and how they affect metabolic rate within one fish. Close, but not what we are looking for.

http://www.masla.com/brackish.html

"Brackish water in a nutshell means a high metabolism."

Compared to what? It's a marine site, so does this mean brackish fish have a higher metabolism than SW fish (according to this guy)? If so, this is sort of the opposite of what you are claiming. The rest is info on how to take care of brackish fish.

Found here: http://hsc.csu.edu.au/biology/core/bala ... .html#net4

TO me That means more energy spent which means higher metabolic rate.

I don't think this is necessarily true. FW fish spend a great deal of energy keeping the solutes inside their cells, just like SW fish spend a great deal keeping them out. I don't know that the difference is a significant one.

Here's another.
http://www.publish.csiro.au/paper/MF98130.htm
Now whatch and see I have probably just hung my self with my own links by not understanding scientific terms! LOL!!!

Now we're getting somewhere! This is regarding what we are discussing by comparing two closely related fish that occur exclusively in SW and FW in nature. But look at what it says:
"Slopes of the regressions relating oxygen consumption rates to body mass did not differ significantly between species and among salinity treatments. Oxygen consumption rates of S. fluviatilis (a freshwater blenny) in FW were significantly higher than in IOC and SW, whereas oxygen consumption rates of S. pavo (a marine blenny, same genus) were similar in IOC and SW salinity but were significantly lower in fish in FW."
In other words, fish kept in their natural salinity or at IOC exhibit what we will call "normal" metabolism. If they were kept in salinities differing from IOC or what they are found in in nature, their metabolism was significantly lower, regardless of whether the change was an increase or decrease in salinity. This is intuitive--stick a marine fish in freshwater and it will stress it out. The most important part is in bold though--the saltwater and freshwater blenny had the same oxygen consumption rates in their natural salinities.

http://groups.msn.com/Breedingtropicalfish/osmoregulation.msnw

This is more about the effects of a changing salinity on a single fish and its effects on stress.

I think I will email my old prof Joe Cech about this. He (literally) wrote the book on Fish Physiology so hopefully he can shed some light. I really would like to find out for sure.

Regards,
Matt

 

[Anonymous]

OK, so in the end is pH <-> ammonia and oxygen? Also, maybe the worry of having high DOM?

I guess that they can be taken care by a huge fuge with macroalgae (plant life) .

M.

Uh, what does <-> mean? :lol:

pH increase favors the formation of ammonia (bad) over ammonium (harmless)

pH increase decreases the amount of O2 that can be dissolved in the water.

Edit: I am not positive that a pH increase alone will decrease oxygen solubility in water. It may be the solute (sea salt) increase that causes it, but for our purposes the latter statement is true.

 

[cjsrch]

ammonia is more toxic in salt water ( well at the ph that salt water is at)

fish are bigger also and remember a 3 inch fish is not equal to 3 one inch fish... inches per gallon and such are more for the ppl who work at an lfs that dont know much ( also its for wal mart employes)

salt water fish are also more territorial usualy

 

[FragMaster]

LOL!!!!
SEE!!! I knew I would hang my self!!!
This is a VERY interesting subject though and one that through soe research you have made me learn a litle more about my hobby!
I love learning new things so dont take any of my responses to heart.
BTW I know you are the site admin. and I know it wasnt an attack! LOL!
I was sarcastic, you just cant see facial expressions through type LOL!!
PLEASE DO ask your friend! I would seriously like to know the true answer.
I still say there metabolism is higher LOL!!!

Yeah thats why I left the 1st part of his question alone! LOL! Had no idea what it ment.
I was only reffering to water volume in my answer back.
Duane


BTW I totaly disagree that salt water fish are usualy mor territorial.
Take a nurse shark for example, heck even a white tip.
the only reason most sharks gather round other fish is either because they are hungry or they are just plain curious. OFCOURSE Iam not speaking about great whites or sand sharks here LOL!.
Most are the exact oposite, save for certain angels, and damsel's.

 

[cjsrch]

"BTW I totaly disagree that salt water fish are usualy mor territorial.
Take a nurse shark for example, heck even a white tip.
the only reason most sharks gather round other fish is either because they are hungry or they are just plain curious. OFCOURSE Iam not speaking about great whites or sand sharks here LOL!.
Most are the exact oposite, save for certain angels, and damsel's. "


in th eocean they have huge areas to roam and when they do school. they can easily get away from eachother if needed.
and i thought we were talking about keeping "normal "fish not sharks. ( which dont seem to get a long with much unless theya re bigger then the shark)

 

[FragMaster]

Bamboo sharks, catsharks, nurse sharks and white tips will leave EVERY othe rfish in the tank alone if you keep them feed.
ESPECIALY a nurse shark. As long as you make sur eto feed them every day they wouldnt bother a blenny.

I was using extreme examples.

The only truely territorial fish in home aquaria for SW are your pygmy angels, certain clowns, pipe fish , and certain damseles.
Thats pretty much it out of THOUSANDS of species.

With fresh water, every other fish is territorial unless you stick to mollies and guppies, and gold fish.