Are Freshwater aquariums just as Biodiverse as Saltwater counterpart?


I've had this question for a long time. As a hobbyist on both sides, I thought saltwater has more biodiversity. But recently I found out that freshwater isn't far behind, though I could be very wrong.

So in SW other than fish and corals, there are a bunch of critter, ranging from microscopic level to visible. You can have a wide range of inverts such as Snails (conchs, trochus, cerith, astraea, stomatella, cowrie...), urchins, feather dusters, sea sponges, shrimps (pistol, skunk, fire red, sexy, peppermint...), crabs (emerald, hermit, halloween, pitho...), pods (copepods, amphipods...), worms, sea slugs, and a bunch of other things that pop up out of nowhere.

I read that in freshwater (aquaria) there are many other little stuff, though could be not as visible as in reef. You can have planaria, hydras, black/white worms, snails, crabs, frogs, even pods,...... The thing is, I've never had all of these in my tank and I did try to look for them. I do have some worms, but they are very very small. My oldest tank is 3 years old and heavily planted.

So in your experience, is freshwater aquarium environment biodiverse? What about in the wild like lakes and rivers?


Get in the wild its a whole different ballgame. A lot of insects are attracted to the water, plus all the small stuff you may be able to see with the naked eye or not. Amphibians, reptiles, inverterbrates, fish, plant life, etc.

The more fun part in the wild to me is watching all the land life interact with the water life.
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I don't know about saltwater, but I would like to also. in one of my fresh tanks. it had no fish, and little flow. and after about 2 weeks, there were thousands of cyclops, worms, daphnia. it was kind of terrifying, but it was also one of my favorite tanks because it was so educational.
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Yeah I’ve always been kind of a saltwater dreamer because corals are so cool! And all of the saltwater invertebrates are great. I didn’t know about all the little worms and pods. I’ve thought about how little bugs like that that could reproduce in my fish tank and feed my fish would be awesome. I’ll have to look into the things that were mentioned here.
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In my opinion, freshwater ecosystems have a lot of biodiversity, even aquariums. We have water fleas, mites, lice, springtails, detritus worms, copepods, flatworms, planaria, tubifex, midges, mosquitoes and their larvae, fungus nat larvae, shrimp, snails, clams, limpets, mussels, parasites, aquatic, semi-aquatic and carnivorous plants, algae including the infamous marimo, diatoms, isopods, leeches, hydra (my favorite), triops, bacteria, amphibians, fungi, fish and much more!

One of my freshwater aquariums is a 5 gal that I don't take care of...that's right, no maintenance yet critters thrive! This "ecosphere" is FILLED with life (very fun to watch) including diatoms, aquatic and semi-aquatic plants, copepods, algae, un-IDd bugs, bacteria, massive detritus worms, the occasional springtail and loads of detritus. The purple waffle and common ivy have nice root structure while the golden pothos has the longest roots at 8" (20cm) long wrapped around a maple rock. It's relaxing at the end of the day to stare into this "little glass box" and see it teaming with micro & macroscopic life!
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The Amazon basin alone has more fish species than the entire Atlantic Ocean. There are far more plant species in fresh water. And, there are over 76,000 species of freshwater insects--very few are marine.

Still, saltwater has a lot more species of things like macroalgae, crabs, sponges, jellyfish etc. than freshwater. Not to mention, I don't think there are any freshwater corals.

So, I guess it sort of depends on what you're looking at. If I was to guess though, I would think freshwater habitats might have more species, because so many freshwater habitats are cut off from one another. This, I would think, would cause more speciation than in the oceans, where everything is connected.
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In terms of phyla coral reefs are the most biodiverse ecosystems, with nearly all known phyla represented (32 out of 34 known phyla). Many of these phyla do not have freshwater or terrestrial counterparts. In terms of numbers of species, that is difficult and depends what exactly you compare. Coral reefs are extremely diverse in species, they probably contain more species per unit area than a tropical freshwater habitat (high species richness or alpha diversity). But if you look at beta diversity (the change in species diversity from one environment to another) and include all the freshwater habitats in the world, which as Mudminnow has said are disconnected each with very different species compositions, then perhaps freshwater species biodiversity would be equal or greater than that of marine diversity.

As for aquariums, that will depend to a degree on what you put in them....
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