Under Gravel Filter

[shiraz]

hi, i would like to know more about under gravel filters. some shops say that u have to use fine sand like C3 or C5 but other shops say that u have to use bigger pieces of sand. i also understand that the sand bed must be at least 4 inches thick.. am i right? is it a good method of bio-filtration for my 2'' tank?

thanks...

[pospeh]

Undergravel filters are not suitable for marine tanks.

The filtration method using 4 inches of sand is a good method. Its call the deep sand bed (DSB) method. All you need for this method is to lay 4-6 inches of #1 size sand on the bottom of your tank.

However, I wouldn't advise you to use this method in a 2 feet tank, whose dimension, I would guess to be 2x1x1.

If you lay 4 inches of sand in a 12 inch high tank, it would look very ugly, as 1/3 of your tank's height will be filled with sand. This method is really only advisable for tanks above 18 inches tall, and preferably 2 feet tall.

I suggest you to use a modified "Berlin" method in which you use live rock as your filtration method. About 5-10 kgs of live rock should be enough. You can then lay a very thin layer of sand (or no sand at all) for decorative purposes.

In either the DSB or Berlin method, you would need to get a protein skimmer. A air driven skimmer should be enough for your 2 feet tank.

[shiraz]

ohh i see thanks for your advise! so what biological filtration method do u suggest for my 2ft tank? i already have an ehiem professional canister filter that has a normal sponge filter and crushed ceramic chips(like a mini sump actually). do i still need a bio-filter like an overhead filter with bio-balls for example to support the canister filter?

[pospeh]

The live rock is biological filtration.

You can use your canister filter in its present condition with the sponge and the ceramic chips. Just remember to clean it once in a while. You don't need overhead filters or bioballs.

So in conclusion, get about 5-10 kgs of live rock, get a protein skimmer, a hood with fluorescent lights (or power fluroescent lights if you can afford it), and your canister filter, and you are ready to keep fishes and the soft corals.

[shiraz]

thanks a bunch pospeh...

[Cedric]

You can use the UGF plates under 6" of C1 sand and do a plenum system instead. Its just as good as dsb!

[Tanzy]

Cedric,

I won't recommend using a UGF plate for a plenum because the water volume is too small. Best is to use eggcrate supported by PVC pipe to about 2" high. I don't know why but I've just read it before, I think it might be sediment collecting in the plenum and depleting the volume.

[Anthony]

hi tanzy u using plenum system rite.

"Best is to use eggcrate supported by PVC pipe to about 2" high"

so i put the green net over the egg crate and pull in the #1

how many inches the sand need to fill up .. izzit 6" of #1sand include or exclude the 2" eggcrate?

[Tanzy]

Ya, I glue the green net down over the eggcrate. You must make sure the sand doesn't get into the plenum so all 6 sides, or at least 5 sides, must be sealed with the net. The sand in my tank is mixed grade, mostly #1, to about 6" including the plenum, in other words, 6" from bottom glass to sand surface. You might want to put in a netting at 2" from sand surface if you intend to keep animals that will dig.