View Full Version : Why undergravel filter?

8th May 2009, 01:55 AM
Hi guys, just raising a question that's been bothering me for the past month or so and I still cant find a good answer. Why do CRS breeders in Hong Kong and Taiwan prefer undergravel filters with 2-4 eheim 2215 filters linked for a 2 foot tank? I thought cons of undergravel filters outweigh the pros? But then again, their CRS are so darn pretty!


8th May 2009, 02:11 AM
Hi Andrew,

this filter combination gives you best water quality with possibility of special modification (with peat, zeolith..) in a shrimp-safe way.


20th Jul 2009, 11:45 PM
so meaning undergravel is good?

always thought that the pulling of waste products to the bottom will just accumulate these bad stuff till it becomes toxic?

enlightenment please.

20th Jul 2009, 11:51 PM

yes: undergravel is good :) The special function of this set up is that all the soil in your tank functions as a biological filter medium, where 'good' bacterias live. They transform waste into nontoxic stuff.


21st Jul 2009, 12:24 AM
True. But doesnt that work if i left my gravel / soil alone. and the beneficial bacteria will also come along and multiply on it, without the undergravel filter?

21st Jul 2009, 12:31 AM
The undergarvel filter needs drift which is produced by an air pump or an canister. If there is no drift, the function is only rudimental.


21st Jul 2009, 12:34 AM
Now that makes sense.


14th Sep 2009, 01:45 PM
There is always a huge confliect about undergavel filter between taiwan and japan, japnese prefer not to use UGF, taiwan most people reckon it's essential

well, UGF certainly decrease the life time of gravel and not so good for planted tank...that's all i know

i am not using UGF because i forgot to set it at first place...haha

27th Sep 2009, 02:46 PM

UGF filters the water by pulling the water flow downwards and thus using the substrate as a filter medium.

The down side is that it also pulls the nutrients used by rooted plants.

The up side is that non-rooted plants should not be affected as much and you don't have to worry about shrimps (especially fries) being sucked up by the filter.

For standard canister filters, some use pantyhose or similiar items to cover up the intake hose to prevent shrimps from being sucked up. Rooted plants can grow much better as the nutrients are still in the substrate.

In the end, it comes down to personal preferences along with the type of tank / plants / shrimps setup being used.

27th Sep 2009, 09:31 PM
I have been using a combo of both ufg and hang over the back filter for years, the ufg is driven by an air pump(not power head) so that there is a gentle suction in the substrate.My thinking is that the waste produced is sucked into substrate and acts a natural fertilizer for the plants, the over hanging filter has carbon and Zeloite in a media bag(stocking can also be used) and ceramic rings on top and a sponge(from sponge filters)attached to the inlet pipe,this traps floating particles,both produce beneficial bacteria ,cleaning the substrate and filter sponge depends on the amount of inhabitants.I rinse the sponge once a month and siphon the gravel once in six months to a year(depending on the population)as mentioned earlier in ash's thread " In the end, it comes down to personal preferences along with the type of tank / plants / shrimps setup being used." just my two bit!!