Why is Saltwater so different from Fresh?

[LobsterOfJustice]

I've been doing some thinking on this topic, and I have a few questions about why keeping a saltwater tank is so different from keeping fresh. A few main things:

1. Live rock. In fresh water, you let the gravel house bacteria, or use a sponge or bio-wheel. Why is there no equivlent of freshwater live rock? Obviously it wouldnt be reef rock, but even if it was gravel or some kind of porous driftwood it would work. If you put dead rock/sand in saltwater and intriduce ammonia the bacteria will colonize, so the liverock we buy is just to speed up the process and for hitchikers (pods, etc). I'm sure there would be neat little freshwater hitchikers... and Ive often been frustrated because in my freshwater tank the only surface area is the bottom of the tank.

2. Clean up crews. Saltwater tanks, especially reef tanks rely heavily on cleanup crews to get rid of algae and detrius. Why is it that I'm vaccuuming the gravel and scrubbing algae in my freshwater tanks instead of having some kind of cleanup crew. I know freshwater snails are sold (I have some) but most tanks do not have any inverts of any kind.

3. Sumps. Sumps are hardly ever used in freshwater tanks, unless they are very large. Sumps are almost a given with saltwater tanks, and even people with 20G tanks have sumps. All the benefits of a sump in a saltwater tank should still hold true if the water lacks salt.

4. People use power filters and canister filters. Does the problem these pose in saltwater just disappear in freshwater? Why dont we just let the bacteria in the tank do it like in saltwater?

While on the topic of filtration:

5. Why dont skimmers work in freshwater? Or do they?

I've been wondering these things for a while, if anyone has any answers for me I'll apprecieate it.

[chrali]

I don't think freshwater foams nearly like saltwater does which is what makes the skimmer work.

[Randy Holmes-Farley]

To follow up, it is the salt itself in the water that helps drive organic materials from solution. Many organics are less soluble in salt water than fresh for this reason, hence skimming the same organics from water usually works better in seawater.

[mthedude]

Wow, I bet this one is going to get a lot of responses. here's my take:

Fresh doesn't have near the amount of delicate life that saltwater contains. Freshwater can allow a buildup of nutrients and still be safe for the aquatic life. IE power filters, or nitrate factories as I like to call them, will do fine in a fresh tank.

Bacteria is bacteria. It grows under, in, on top of and below any hard surface it can attach. You could put playground sand in a freshwater tank and you would grow some of the same bacteria found in saltwater. You could also buy dry dead rock and add it to a fresh aquarium and bacteria would grow on it and in it, thus making it "live" rock, but not nearly to the extent of fresh water.

You can get algae eating freshwater fish, shrimp and lobsters, but again, the amount of inverts in fresh as compared to salt are going to be very different.

Lots of people use sumps on freshwater tanks and some people run w/out sumps on reef tanks so it's really a matter of personal preference in some cases.

Skimmers only work w/saltwater because it contains elements that make the water foam when exposed to high turbulence (ever seen the foam on top of waves as they wash into shore?). You won't see too much foam on a lake or a river because it does not contain the same buffering compounds, salts, elements etc.

Hope this helps.

[derrikd]

intresting topic

[H2OLUVSME]

1.) the use of plants in FW is similar to me, to the use of LR in SW. i use lots of plants in all of my Fw tanks to help control nutrient levels naturally. i do use a lot of wood in my tanks also. i never thought of them as bacteria housing though. like stated above the SW animals are much more succeptable to nutrients and the last step of denitrification is not that important in Fw setups, IMO.

2.) on the clean-up list, there is a huge difference in the amount available for SW and FW. you can however find a good variety of cleaners for FW. i have a few different types of shrimp (common algae eater, amano shrimp, and of course, ghost shrimp). also i have a planted tank with a few pieces of wood floating. in those tanks i like to keep fiddler crabs. they do a killer job on dieing plant matter. i have seen a few other crabs available in my LFs for FW use also. my fiddlers are one of the coolest inhabitants of my 110 paludarium, in which i have 2 kinds of shrimp, 2 kinds of crab, and some aquatic frogs (who also feed on dead/dieing matter). i particularly dont like the snails (cause they eat my plants and breed like crazy) but i do keep some in my paludarium as a supplemental clean-up and food for my loaches.

3.) ive thought of the same thing here. i wanted do design a system with no visible equipment in the display. this is the only function i can see for a sump in FW, being that the water quality doesnt seem to be trouble without one. after setting up quite a few Fw tanks i have found ways to hide the little equipment that is really needed to run these systems successfully.

4 and 5) i think these were covered above. 4.) no need to gert rid of the nitrates 5.) skimmer doesnt work without salt......

i cant wait to see what otheres use as clean-up in there FW tanks, if any.

great thread hope i helped.

landon

[Shoestring Reefer]

I agree with mthedude, this should get a few responses.

My experience/opinions:

0) Keep in mind, a SW FISH tank and a SW REEF tank are two different things. Also, when people get into SW, they expect to get more (and more complicated) "stuff", and get more biodiversity.

1) You can have all sorts of stuff in your tank, so the only surface needs not be the bottom. Many ciclid tanks have lots of rock; in fact, rock structures are common in lots of FW tanks. Get some holy Texas rock from Ebay. As far as hitch hikers: I agree, that doesn't seem to be a focus in FW, but that's just the FW culture.

2) I had a FW planted tank and, like H2OLUVSME, I've had amano shrimp (great for FW hair algae) and I know there's a lot of other clean-up animals available-fish, snails, shrimp, crabs.

3) I agree, but IMO that's just a cultural difference between FW and SW aquariusts.

4) Not much to add, wish I could.

5) SW Skimmers don't work in FW because the foam doesn't build. It has to do with teh surface tension of teh water. BUT there IS a company that sells FRESHWATER POND SKIMMERS. And I mean FOAM FRACTONITIONERS, not surface skimmers. They are basically a short neck, wide body skimmer with many, many small tubes packed into the skimmer neck. I wish I remembered which link it is, but I remember it's a British company.

[adrinal]

First you need to remember that heavly planted tanks and FWFO tanks are worlds apart. Planted tanks with few fish can be done much more naturally.

When I lived in Asia, there were many tanks that simply had a huge sump and algae export systems.

I think the reason we dont see lots of rock or stuff in the tank, and sumps and what not is... you don't need to. Folks only add clutter, complexity and expense to things when you have to.

[jgln]

Not arguing here, it's just I actually thought the foaming was not just due to bubbles but how "dirty" the water is. I live in NJ and spend a lot of time by the ocean and notice when the water is dirty there is lots of foam and when clean not so foamy. This usually cooresponds to the water quality not how big the waves are. Sometimes sewerage backing up into the ocean (don't swim in foamy water) . I've also seen fresh water with foam and it WAS dirty. Beleive me, a nice dirty FW river does foam. In fact, and I don't mean to be crude here, I thought that is why "pee" sometimes foams more sometimes than others. Sometimes it's "dirtier" than others. I guess I was wrong? Didn't know salt had anything to do with it.

[brad23]

I have a freshwater and just have loads of rock in it and no plants, it's a african cichlid tank. They have to be the most messy waste producing fish there are.

All I have on it is powerfilters and have 16 cichlids in a 75g and hardly have any Nitrate in the water.

[Randy Holmes-Farley]

Not arguing here, it's just I actually thought the foaming was not just due to bubbles but how "dirty" the water is.

The foaming comes from the effects of organics being forced to the air water interface by being less soluble in the salt water than in fresh.

Totally pure salt water with zero organic material will not foam.

[nitroxadvanced]

wow.... there arnt any real hitchhikers for FW except paracites..

[FMarini]

Well to me the only difference between a SW tank and a FW tank is the Salt and the fish. Otherwise its pretty much similar if not the same stuff.
1. Live rock. if you want a place to house bacteria any substrate will work. reef keepers like the "look" of a natural environment, so they add rock. Fw people add local "holey rock" or logs or whatever to simulate streams, river etc. same thing really. deep sand beds house bacteria as well, as do the colored pebbles in a FW tank.
Also the plant tank comparision is a great one to a reef tank. deep substrates to house bacterial, and infauna, plants to provide denitrification.
believe me the surface area of everything in your tank is a place for biofilms (bacteria) to form.

2. Clean up crews. we have clean up crews in fw tanks too. Many are shrimp, snails, loaches, plecos. All these critters job is to move detritus, and clean up waste. I even have filterfeeding shrimp from cameroon in my FW planted tank that removes free floating FW algae (phytoplantons so to speak) and keeps the water crystal clean. Now in cichild tanks, the fish are too mean to keep a decent clean up crew- just like keeping triggers and puffers in a SW fish tank.
Hitchhikers in FW-sure thing, snails, worms, hydra, some good, some not so good.

3. Sumps. sumps just haven't caught on w/ the FW crowd for whatever reason. I have sumps on my Planted tank. But in general we SW people use them to remove unsightly equipment and provide much greater water volumes

4. People use power filters and canister filters. SW people don't like them becuz they are ugly, and don't want extra stuff hanging off the tank- its more of a mind set thingy. I have many friends who started their Sw tank using hang-on filters, and UGF just like FW keepers

5. Why dont skimmers work in freshwater? Or do they?
They do..in fact foam fractionators where intially invented to remove organic waste in waste water treatment plants (Fresh water).
To skim in FW you need 2 things, more air and more waste. The surface tension of the Sw allows smaller air bubbles to form, hence create more surface area and organics are more readily driven out of Sw than FW, and hence the reason why people can use low powered air skimmers on Sw tanks w/ ease.
Anyone ever use a Bullet skimmer or any beckett headed skimmer? A becket head was designed to remove the surface scum off of farm ponds and provide cleaner water. If you take a Bullet skimmer w/ a high power pump full of organic laden FW water- it will foam up and skim,
So to me its a mind set difference... believe me I've seen FW planted tanks that easily rival any SW reef tanks, and vice versa

[bronzermike54]

i bought a 350 G acrylic tank last year from a guy who had piranha's in it. He had it rigged with a sump and 2 Iwaki pumps. I converted it to SW use, but it was using a sump with FW> I also have a 110 g tall FW tank. It is full of Holy rock, which is ALSO a surface area beyond the gravel bed.

[albinooscar]

Originally posted by Randy Holmes-Farley
Not arguing here, it's just I actually thought the foaming was not just due to bubbles but how "dirty" the water is.

The foaming comes from the effects of organics being forced to the air water interface by being less soluble in the salt water than in fresh.

Totally pure salt water with zero organic material will not foam.
Let me help! let me help!

The way I see this is that saltwater is denser than freshwater which makes the organics more buoyant in saltwater so they just float around in the water column and that's why the process of skimming work.
Because freshwater is less dense than saltwater the organics tend to sink to the bottom in freshwater, hence the UGF.

Ron

[Lost His Marbles Name]

Originally posted by albinooscar
Let me help! let me help!

The way I see this is that saltwater is denser than freshwater which makes the organics more buoyant in saltwater so they just float around in the water column and that's why the process of skimming work.
Because freshwater is less dense than saltwater the organics tend to sink to the bottom in freshwater, hence the UGF.

Ron
The dead sea has more salt in it then any other body of water. You can almost float on top of the water due to it's density. Stop me If I'm wrong.
I also have FW and the fish popo sits on the bottom untill I clean the gravel or one of the three filters take it in. I wish SW was as easy as FW and less expensive.

[adrinal]

Originally posted by nitroxadvanced
wow.... there arnt any real hitchhikers for FW except paracites..

Depends if the place is fed by rain water or in a stagnate pond.

There are tons of critters in most fresh water bodys though.

[Irish Mortal]

In my opinion, the reason for the vast differences between the FW side and SW side of the hobby has to do with their respective natural environments.

Look at the biotopes of most freshwater fish and you will see that there are large fluctuations in their environments daily, seasonally and yearly. This, I believe, is why FW fish are more hardy in general and do not require as much support equipment to keep alive. Creating an accurate thriving boitope for, say, Discus taskes less effort and support equipment than maintaining a reef tank. This is not to say that rearing Discus, or many other FW fish is 'easy'. It still takes quite a bit of effort. But, because their natural environments are not as constant as most tropical reefs, we do not require as much equipment. For example water temps lighting and water chemistry will vary widely. Look at the Amazon basin through the diffent seasons.

SW, on the other hand, organisms have had millions of years to evolve into very specialized niches and may not be able to survive outside of their normal environment. ( The Amazon basin has not existed very long at all, on geologic scale) Many corals and some fish have evolved into VERY specialized biologib niches in order to survive and proliferat amonst the competition in the sea. Also, the worlds oceans are such great volumes of water that it is very hard to alter the chemistry of the water. We as humans have recently been able to but that's another discussion.

That's just my take on it. I base this on my reading about the environments of the fish I keep and on observations having had both planted 'high end' FW tanks and reef tanks.

Sorry for the wordy reply.

[jgln]

Thanks for the explanations. But I'm probably just going to have to set up an experiment and prove this to myself. Not that I think you're wrong at all, just like to see it, I'd find it interesting.

[Randy Holmes-Farley]

The way I see this is that saltwater is denser than freshwater which makes the organics more buoyant in saltwater so they just float around in the water column and that's why the process of skimming work.
Because freshwater is less dense than saltwater the organics tend to sink to the bottom in freshwater, hence the UGF.

Sorry, I don't think gravity has anything to do with the attraction of organics to air/water interfaces. If you take a bottle of beer, you don't get alcohol on the bottom and water on the top. Entropy and water motion drive dissolved molecules throughout the water column, regardless of their "density".

Thanks for the explanations. But I'm probably just going to have to set up an experiment and prove this to myself.

Many of the other issues might need to be "proven", but there is a vast scientific literature on skimming and when and why organics bind to air/water interfaces. As folks have said, you can skim fresh water, but not as well for well known and established reasons.

[Saltz Creep]

It is freshwater that is different from saltwater. Life evolved in saltwater first and later adapted to deficient freshwater.

[Heinz]

there is a freshwater skimmer (http://www.schuran.com/freshwater/abschaeumer_e.html)

[DeepCutta720]

I had this same debate in my mind when I started my salt water tank. I think it all comes down to whether you want to do a Fish Only or Reef tank. If your tank is going to be a fish only tank then its really no different than a fresh water tank if you ask me. For my fish only tank I applied fresh water principles with out any issues. I also saved a great deal of money. My salt water setup was not any more expensive than my identically sized fresh water tank. Up keep is no more expensive either considering I use RO water for the fresh water tank as well. I had a very limited budget when starting this tank. What you see below in the pics was started for $350 including the live stock and stand etc.

A fish only tank really is just a freshwater tank with salt. I actually think the salt water tank is easier to maintain than my fresh water tank. I used to modify the pH and softness of my FW tank. With my SW tank the aragonite and limestone base rock buffer the pH and the marine salt I use maintains the correct pH for me. Its always at 8.1-8.2 whenever I check with no additives. Those are two things right there I dont have to worry about anymore that I used to in my FW tank. I use the same heater and the same Aquaclear HOB power filter. I treat it just like a skimmer collection cup, I clean out the filter sponge every week to make sure it doesnt become a waste trap. I buy RO salt mixed water from the LFS once a month before I do my water change. I keep my light on only when I am viewing the aquarium just like my FW tank and have had zero algae issues. My water parameters have been fine since I cycled the tank. I siphon the bottom of the tank just like I would my FW tank when doing water changes. In the end from scratch, I spent about $350 for my 20gallon long sw tank. This included stand, tank, lighting, hood, filters, heaters, rocks, substrate, additives, water, livestock etc. It has been running for weeks now very well and has one fish. To me, my tank is really a fresh water tank with salt.

Obviously, this all changes as soon as you want to keep corals and rich invert life. =)

here are some pics of my fish only tank:

http://members.cox.net/asiddiqui/tank.jpg <br>
http://members.cox.net/asiddiqui/chiliIc2.jpg <BR>
http://members.cox.net/asiddiqui/chiliIce1.jpg

[Saltz Creep]

I'd trade the plastic plants for some LR to seed the base rock with coraline.

[Shoestring Reefer]

I like the flowers. They go well with the fire fish. :)

[Bomber]

Why is Saltwater so different from Fresh?

For the most part it's only because some things that are not as toxic in fresh water are toxic in salt.

[LVfishguy]

I really have to dissagree with many of you on saying that nitrates are not a factor in F/W. Yes, many of the fish can handle a lot of abuse as far as water quality is consered but, does it mean that it is good for them? That is the problem with many people in F/W. They "get away" with doing less what people will do with there S/W or reef tanks.
Many people that are into fish tanks. Start with F/W and as in any new hobby do not want to break the bank getting into it. Thus, you see very few wet/dry systems ect. I know just as many crazy F/W people that have huge systems with auto fills, and many of the toys that reef people use. It is just rare to see. Most of these people have an appreciation for the fish and are not just looking for something pretty. And many of them create whole F/W biotopes from different regions of the world.
Anyway, I am rambling now. I guess what I am trying to say is that there really aren't many differences as far as the principles are conserned. It is just mostly in the application.

[Flipper1]

AFA skimming for FW, I'll point out an experiment I did with my 5-1/2 year old daughter, who's been learning the SW and FW hobby with me since she was 2 (and believe me, they understand and retain a LOT at this age!). She asked me about the skimmer one day, so I did this:

I filled two glasses 1/4 full each; one with water, one with milk. I pointed out to her that the milk IS water, but has many other organic components ivolved; thus the color, thickness, etc. I gave her a straw and told her to begin blowing bubbles into the milk. Within a minute, the glass was filled more than half way with foam. We took a clean straw, and she did the same in the glass of water. Of course there were lots of bubbles, but no foam.

She got the basics from this.

[Frick-n-Frags]

IMO, there are several things:

1) The life on the reefs evolved to a very tight and constant set of conditions and therefore cannot tolerate big physical differences as well as the more flexible freshwater critters.

2) The salt conditions force the animals to work harder at keeping their bodies working correctly which includes major expulsion of salt and better O2 collecting abilities. Thus they have less survival slack to put up with harsh conditions. Life is just easier in fresh water.

3) Toxins(especially metals) can be dissolved into saltwater more easily so no brass fittings or lead weight strips etc.


FWIW, skimmers also work in saltwater better because the water has better surface tension and can support the fine bubbles from a skimmer which would not last in fresh water. A skimmer won't work even in a really crapped out FW fishtank.

[Bomber]

Foam fractionation is common in fresh water aquaculture outside of the hobby. They are just built a little different for fresh water.