Thread: Adding Extra filtration after nexus/pump fed filter

Does anyone have any experience of seeing,or running themselves, an additional filter on the gravity return from a pump fed filter? Particularly a nexus

Can’t find much online but hoping someone can chip in maybe with some pics if possible?

Obviously I know it’s not a popular setup, due to heights amongst other things but thought it may have been done before?


My current setup is retro drain to uv then a sieve which feeds into nexus which then discharges into an upper pond/veg filter before returning to pond via blade

I’ve had problems with ph/kh so I’m going to add oyster shells but don’t want to just dump the bags in the veg filter so was thinking of sitting an extra filter within the veg filter and running the nexus return into that before overflowing into veg filter

Not sure if that makes sense? Can do a basic sketch if not, any opinions welcome


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That’s helpful cheers, looking at the diagram of yours I guess mine would be the equivalent,position wise, of your outlet chamber-where you have the heaters?

Overflow probably isn’t too much of an issue as I plan on siting the chamber within the upper pond/bog filter so in the event of an overflow it’d just go into there anyway

Do we think I would be able to have the nexus return entering into the base of the box and use it in an upflow style? Bearing in mind the return is gravity-I don’t want the added pressure to back up the nexus?


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Originally Posted by Alburglar

A sieve could work.
Bog filter
Plant bed
Anoxic chamber

I do already have a sieve before the nexus, im just really looking for somewhere to site these oyster shells -and maybe water polishing floss from time to time-preferably in clean water flow rather than just dumping them in bags in the bog filter


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Originally Posted by Alburglar

IMO - forget onion sacks, the eBay ones I used degraded and split after a couple of years

Glad you mentioned that because I was thinking of going that route,I’ll get the better proper media bags and give them a go!

I’ve had some really low ph drops this year, for unknown reasons-I’ve never struggled with it before-I’ve read as low as 5 which is obviously disastrous and I’ve lost a few fish to it recently so I want to get the shells in there asap


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