freshwater live sand\rock

[Demonknight]

Something I have been wondering for some time now. Why does live rock/sand work for salt water and not fresh? This is assuming I have the basics of salt correct in that the sand/rock do the bulk of the filtering? and it just needs current for it to do its job. One would think it would be the same in fresh as well.

 

[Mebbid]

Buying live rock / sand isn't much different than adding a used filter pad to your tank. Live rock will work for fresh water assuming the water it's going in will have a high enough pH. If the pH is too low the live rock will just dissolve changing the tanks parameters.

I would imagine it's really a cost vs reward process. The live rock is obscenely expensive and isn't necessary in freshwater. However in salt water it has water buffering properties as well as the space for anaerobic bacteria to grow for nitrate reduction.

Also, most live rock is naturally collected and has saltwater microbes and critters on it that will die in fresh water.

 

[Demonknight]

I was thinking more of why couldn't one set up a fresh water tank like a salt tank and use live rock/sand instead of a filter system (this would of course only work once fresh water BB gets going), say a large(ish) pile of some kind of lava rock (lots of holes) in the middle of the tank and a power head pushing water across it for flow. Again if I'm mistaken on how salt tanks work forgive me as I have never had one or looked intot hem much.

 

[Mebbid]

There's nothing saying you can't. It's just that there are more efficient ways of filtering a freshwater tank out there. Saltwater uses a ton of flow (10x - 4 tank volume per hour) to keep debris suspended in the water column long enough for the secondary filtration to remove it (skimmer / sump) Whereas freshwater debris is taken out through the filter and regular cleanings.

You will also have to limit your stocking a bit more.

 

[Fresh2o]

I googled DSB freshwater and found an informative link:
http://www.wetwebmedia.com/ca/volume_7/volume_7_1/dsb.html
Deep sand bed (DSB) should work fine in FW. However, if the goal is to maintain decent water, then it is generally better to remove waste mechanically before it gets the chance to breakdown. I am a bit of a hypocrite with that since I have a planted tank that has been running for about 15 months and I have not vacuumed the substrate at all.

I believe the purpose of a DSB or setup with porous rock as you described is for the reduction of nitrates. But that should not replace the need for regular water changes.

I agree with you in that it would work.

 

[Demonknight]

My 45 is planted (dirt) and is kind of the inspiration for the question, while I do run a canister on it I have to wonder just how much its really doing with the plants growing like weeds.

 

[Luananeko]

I've experimented with lava rock as extra filtration for lowering nitrates and found that they do indeed seem to help, as does having live plants. My 36 gallon bowfront tank has all artificial plants (it's a GloFish tank, so it has blue lighting and all fluorescent decorations... live plants would have thrown off the look), so it normally needed frequent water changes to keep nitrates under control... As an experiment I added one 10 gallon tank plumbed in with a huge pile of lava rock that is a shrimp breeding colony plus one more 10 gallon tank plumbed in as a live plant grow out tank. The nitrates dropped to nearly nothing after a month. Whether that's due to the plants or the lava rock, I can't say for sure, but the plants aren't growing fast enough for me to think that they're the sole cause.

 

[Mebbid]

My 45 is planted (dirt) and is kind of the inspiration for the question, while I do run a canister on it I have to wonder just how much its really doing with the plants growing like weeds.

Polishing the water and handling what little ammonia production there is at night.

 

[Demonknight]

Probably LOL not much it would seem outside of water movement, heres a shot taken tonight that kind of shows how heavy the plants are, this is a 45 tall tank and the swords are sticking out of the water at the top of the tank.