Sump Filtration and Overflow for dripping water change

[Alvin Leung]

Hi all,

I am setting up a new tank with a sump filtration similar to the one Mr. Soestbergen has designed as in:

The water from the main tank will overflow into a chamber built in one of the back corner and the overflown water drops into the sump filter.

To improve water quality, I intend to change about 25% of tank water daily by dripping new water into the system and let surplus water overflown out of the system. A lot of local breeders here in Hong Kong use this kind of water change, some have even no filter at all, just relying on this gradual water change to remove water products.

My questions are:
1) Will 25% or more water change daily reduce the efficiency of the sump filter? Some people I ask said the biological filter will not work with daily water change.

2) Imagine I am just using a bare tank for fish (without filter) and I want to use the drip system for water change, I would drill a hole on the back of the tank at the water level line so that any new water dripping into the tank will displace the same volume of tank water out from the hole. Right?

Now if I use the sump filter like I mentioned above, where should I drill the overflow hole? Obviously not on the main tank as it already has a overflow hole to lead water from the tank into the sump filter. Shall I drill in chamber 6 in Mr Soestbergen's diagram? If yes, how high?

Thank you reading my long post.

[Fred Goodall]

Hi Alvin

25% daily should not stop biofilter working... should just cause "filter bacteria" to adjust population to "available food"

Can not where hole should be drilled since can not say "flow pattern and mixing pattern" for water in your system... but "on average" should be ok anywhere you choose as long as "inflow" and "outflow" not very close to each other. Picture bathtub... water drain and faucet... fill tub... add hot water at 'drip' and let water drain out... "overflow" / "spill rate" and "location" / "current" play big part in how well system works... we can say is that drip system is "best" and biofilter on drip system is "double safe" thinking / method.

So... drill where convient for your needs and make "improvements" when needed. "water in" usually displaces equal amount "out" .... and when dealing with "overflow" setup... "headroom" not factor for "displacement". So yes, dripping in will remove equal amount of water.

[Mark Evenden]

25% is fine, what you have to get your head around is that its not like turning everything off, draining 25% and replacing it.

My system changes 10% in a 24 hour period, the only difference is my filter are now 17 years old and did run on a closed system for 12 years before I converted to an over flow.

I do periodically run the system for a week with no water change (usually when lightly stocked, and likewise increase the flow when I have higher / new fish.

Thats the beauty of a system, its so flexible!