Filtration capabilities of sand/gravel

[African_Fever]

With the 'updated' thread on the silica sand debate brought to light, it's good timing as I've actually been thinking about this quite a bit lately; how much actual filtering capacity or capability would a layer of sand or gravel provide to a large tank? (I know sand would provide much more due to the larger surface area per volume) In even a 6'x2' tank a 5 gallon pail would just cover the bottom of the tank, no where near even an inch. Yet think about the filtering capacity (I'm talking purely biological here) of a 5-gallon pail sized filter - essentially an FX5 or larger. Keeping a thin layer of sand, the rays would still this up regularly, and with the high flow rates of so many filters/pumps/powerheads everyone uses in their ray tanks, there would be quite a bit of flow over this sand.

I'm just looking for everyone's opinion on this this idea of using sand (even if just a skiff) for it's biological filtering capacities.

 

[PoopSmart]

I always wondered why you couldn't use gravel as media in a filter, is the bio media usually more surface area than sand or gravel? I mean i want to just fill up a filter basket with my old gravel from my established 29 just for safety, but I never asked the question.

I want to know this too.

 

[African_Fever]

Bio media does have much more surface area than gravel does, but I don't see why you couldn't fill up a basket with gravel. It would theoretically work just as well as squeezing an established sponge over the new filter media. A fluidized bed filter is just a pressurized filter that keeps silica sand suspended in the water column.

 

[Nic]

I run over 15L of submerged media in my sump.... 1 gallon of bioballs in a old skimmer and a fbf300... I don't worry about needing more bio media.. I plan on icreasing my submerged media and filling the skimmer with either matrix or substrate pro... I'm also gonna add a 2nd Fbf filter I'm debating between the 300 and the 600...

 

[African_Fever]

Nic - If you're not worried about needing more bio media, then why are you planning on increasing it? I'd say obviously you are interested in more bio media.

15L of submerged media (I'm not sure what you're using) in your sump isn't all that much when you look at the volume of sand/gravel you could easily have in a thin layer in your tank (again, I don't know what size tank you have). It's not even 5 gallons of sand, and 5 gallons of sand would barely be a skiff across the bottom of a 6x2 tank.

I'm not trying to raise anyone's feathers or anything, I guess just wondering why everyone is keeping their rays in bare bottom tanks? The way I look at it, is even the thinnest skiff of sand across the bottom is going to provide at least a bit more biological filtration, and most likely make your rays feel at least a bit more at home, while not being thick enough to make keeping the tank clean or anything like that an issue. I've only been keeping my rays a year, but I've kept fish long enough to see that they're definitely more intelligent than most other fish, and I wonder if bare tanks themselves would somehow 'stress' the fish in that they never have any cover (nothing to bury themselves with), and no interaction with anything besides themselves and their tankmates.

Just something I've been thinking about lately after watching my two motoro's and how much their behaviour has changed after getting into a much larger tank.

 

[Nic]

Nic - If you're not worried about needing more bio media, then why are you planning on increasing it? I'd say obviously you are interested in more bio media.

15L of submerged media (I'm not sure what you're using) in your sump isn't all that much when you look at the volume of sand/gravel you could easily have in a thin layer in your tank (again, I don't know what size tank you have). It's not even 5 gallons of sand, and 5 gallons of sand would barely be a skiff across the bottom of a 6x2 tank.

I'm not trying to raise anyone's feathers or anything, I guess just wondering why everyone is keeping their rays in bare bottom tanks? The way I look at it, is even the thinnest skiff of sand across the bottom is going to provide at least a bit more biological filtration, and most likely make your rays feel at least a bit more at home, while not being thick enough to make keeping the tank clean or anything like that an issue. I've only been keeping my rays a year, but I've kept fish long enough to see that they're definitely more intelligent than most other fish, and I wonder if bare tanks themselves would somehow 'stress' the fish in that they never have any cover (nothing to bury themselves with), and no interaction with anything besides themselves and their tankmates.

Just something I've been thinking about lately after watching my two motoro's and how much their behaviour has changed after getting into a much larger tank.

seachem matrix @8L 3L eheim substrate pro... and a mixture of bio rings old gravel eheim lava rock etc.. i guess 15L but it is probally alot more plus add the skimmer filled with media as well ..... my tank uis always going to grow in stocking and this filter will be transferred to my new tank this summer.... so im gonna add alot more bio.... before problems showed up that system supported 7 widebar dat5 -14" , 1 black aro 16", 2 14" tropical gars and my 3 rays 1.1 motoro and a 9" tiger ray.... my params were always perfect and i feed very heavily ... my decision to increase is based on my upgrading of tank and stock.... my total system capacity is 250 gallon... bare bottom allows me to keep my tank cleaner...