Question Beginner Filter Questions

Scarletfire

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From everything I read, live rock is the SW biological filter. Why can't sponge filters do the same? Not sure the pro vs cons of the sponge filter. Wouldn't sponge filter be more porous than rock?

With live rock, I see people still have external filters. Is this mandatory? I've read in different places that the live rock is the only filter needed.
 

stella1979

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I cannot wait to share my personal experience with you... I'm sure there are many opinions on this and I'll be very happy to put in my two cents when I can get in front of my pc this afternoon. I'll be back but in the meantime I'll say this... I have a 20g long mixed reef with 20 pounds of live rock (was dry rock at purchase) as well as an HOB with biomedia inside. The filter is also capable of holding a floss or sponge for mechanical filtration and this media would, of course, hold beneficial bacteria so could contribute to the tank's cycle. However... I'm not running mechanical filtration these days and that is because it quickly gets 'dirty', holding onto decaying organics, and is thus a source of nitrates and phosphates... food for algae. To keep algae at bay when running mechanical filtration, I have to change that floss pad out for a clean one every few days. There's not always time for such regular upkeep so... sometimes we just leave that floss pad out.
More later!
 
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Scarletfire

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More later!
I can't wait!

Also, I don't understand why it's an issue in SW and not in FW, and a lot of people have sumps too (I guess for ease of changing filter pads?)

And wouldn't a protein skimmer also leave. Lot of stuff in it that will decay as well?

And if the stuff isn't removed from the tank into a filter, wouldn't it be just dying in the tank where the rocks are?
 

Lchi87

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Nitrates are more of an issue with saltwater which is why anything that has the potential to accumulate a ton of gunk and turn into a nitrate factory is to be avoided. Fw tanks for the most part are fine with a moderate amount of nitrates especially planted tanks but in most cases in the salty world, we like to keep our nitrates on the low end, say around 5ppm. Of course you’ll find people who have reef tanks with higher nitrates that still do “well” but here we have to remember that all tanks are unique and what may work for one, could mean trouble in another.

Skimmers collect the nasty stuff in an external cup so that it is no longer in your water

As for detritus and things like excess food, a clean up crew takes care of that, which is why most reef tanks will house an array of snails and crabs. They consume detritus and bits of food (and some algae) so that they aren’t fouling up your water.

Hope that helps to explain things a bit!
 
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Scarletfire

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It does a bit, actually. So, what's the equivalent of plants in SW? What do I grow to eat up the carbon of I can't grow plants? Do I buy plankton, or does it somehow develop when trying to cycle the tank?
 

Lchi87

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The equivalent to plants? Depends on what you mean... if we’re talking about things to grow that look pretty, I’d say coral lol but if we’re talking about something that exports excess nutrients, I’d say chaeto! It isnt carbon that we don’t want. Its high nitrates and high phosphates. So back to chaeto...Its a common type of macroalgae that reefers specifically keep that helps to eat up nitrates in your system. Phytoplankton is something that corals eat and can be bought from the refrigerated section of your LFS or can be cultured yourself.
 
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Scarletfire

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The equivalent to plants? Depends on what you mean... if we’re talking about things to grow that look pretty, I’d say coral lol but if we’re talking about something that exports excess nutrients, I’d say chaeto! It isnt carbon that we don’t want. Its high nitrates and high phosphates. So back to chaeto...Its a common type of macroalgae that reefers specifically keep that helps to eat up nitrates in your system. Phytoplankton is something that corals eat and can be bought from the refrigerated section of your LFS or can be cultured yourself.
Ah okay. Macro algae. I'll do more research into that..

Seaweed XD

I just kidding
Oddly enough, I was thinking that, but I never see seaweed in the photos haha
 

stella1979

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Alrighty... here's my thinking on all of this. So sorry for the delay.

First, live rock isn't just for maintaining a cycle. When folks talk about a mature tank, what they're really talking about is the presence of all kinds of microfauna (and sometimes flora) that would also be found in the wild. Just like many FW fish like a well planted tank, or how our favorite FW shrimp and snails need that biofilm an established tank provides to really thrive... well, things like copepods and amphipods will not sustain a healthy population without their living space, and that is, the pores of the rocks. Also, many hardcore algae eaters will feast on glass and equipment... but my clownfish will only pick at the rocks for his little bits of greenery.

Here's a story on why having your cycle in the tank can be a real lifesaver... I live in Florida, where hurricanes are a fact of life. When Irma came through a few years ago, we didn't have power for more than a week. Without flow, corals would start to die, and without a cycle, the tank would soon become poisonous to its inhabitants. So, we couldn't run the filter, but we could hook one of the pumps up to a car battery. Providing that flow kept the corals from going too far downhill, kept the water from getting dangerously hot via good surface agitation, and also due to the flow in the tank, the cycle from beneficial bacteria within the rock, remained stable. Meanwhile, I had freshwater tanks that were thankfully less sensitive, because I could not power them at all. The cycle was lost in a quarantine tank and nearly so in a goldfish tank.

Anyhow, for those reasons, I would say rock is very important for stability and stability itself is of the utmost importance for all fish tanks... though, I'd say especially so when sensitive little inverts and corals are involved.

As for the whole "mechanical filtration turns into a nitrate factory" argument... well, it's only true if we let it be true. Indeed, the build-up of detritus or excess nutrients anywhere in the tank or system is a recipe for algae problems. However, in case you haven't noticed, I'm all about that flow. My 20g long has an Aquaclear 70 and two powerheads pushing at least 500gph each for a total tank turnover rate of about 30x the water volume per hour. Gunk certainly doesn't settle as easily as it would, say, in a betta tank. However, there are areas in the tank where the rocks themselves create what we call 'dead spots'. These areas get blasted with a turkey baster or even a mini pump before each water change in an effort to suspend stuff that has settled there. These areas are also favorite hangout spots for the clean up crew.

Okay, well, this is certainly getting longer than I intended. Idk a simple answer as to why certain things are okay for FW and not advised in SW but the overall thought based on my experience is that nuisance algae grows faster in a marine environment and while that's bad enough, perhaps worse is the sensitivity of some critters to elevated nutrients. My old goldfish was a-okay with a nitrate level of 30ppm or even a bit higher. Now, I haven't tried it, but I imagine my corals would be unhappy with a similar level of nitrates and here's the reasoning for that... Imagine a pond or lake's natural water quality where fish and plants contribute to nutrient levels and sadly, so too does pollution, agricultural run-off, and so on. Now, imagine the oceans which suffer the same things... but with oceans being vast, there is so very much dilution. I'm pretty lucky in location I suppose... living in South Florida has given me the opportunity to see such things in nature... and yes, I've done nitrate and phosphate tests on natural bodies of water. I cannot find these nutrients in ocean water but I have seen very high levels in lakes and ponds, even those as far from humans as the swamps in the Everglades. Anyway, the point is, with my salty tank, I'm trying to create a little piece of the wild ocean, and the goal is to offer tank inhabitants the conditions which they'd find in the wild.

Phew... sorry for wall-o-text, but there are my thoughts on these matters. Fun discussion, yeah?
 

Wild Bill

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3 words. Great Salt Lake.
I live in Utah. The Great Salt Lake has entry but no exit for water, that’s why it has a greater salinity than the ocean. So the only filtration it has is the rock in the water (which in not much) with sponge filters, you cannot clean them good enough to create an environment for your fish to survive.

Most fish sold in the hobby are raised in an environment that is fairly stable unless “wild caught”. If those fish were to be released into the wild, they would die pretty fast because they are not adapted to the “wild conditions”.

The Great Salt Lakes only inhabitants are brine shrimp because of these conditions. The water is not clean enough for fish or corals for that reason. I hope this gives you some information on what your asking.
 
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