Adding a secondary filter - mainly for polishing

[Sleeveless]

On my 75g, I have a Fluval FX4 with the intake/output on the left side of the tank. The outputs face 1 to fire to the right side of the tank and the 2nd 90 degrees off that one to fire to the front. I have Purigen and polishing media in the fx4, but if there is ever a need to treat the tank and the larger need to replace those polishing pads every 30 days as they build up with quickly I was thinking of adding a second, HOB filter on the right side of the tank to just hold filter floss and purigen. Question is, if I go this route, should I spec a filter for the same level of turnover as my primary or is something a little smaller sufficient. Example: I was looking at the Fluval AC50 which is a little under for a 75g.

Just looking for some opinions since I've seen postings on FB about this topic, but never asked the question about sizing.

 

[Rusty_Shackleford]

I probably wouldn't go through the expense of another Fluval, especially if you're looking for some to just polish the water.

I would do this. Run it for 24 hours once in a while to polish the water and then take it out till next time.

Amazon.com

a.co

 

[seangee]

SInce you don't need more filtration capacity isn't really a factor. More important is flow and ensuring you don't introduce unwanted turbulance.
I have no idea what fish you have or what the tank looks like but do you actually need purigen and polishing pads running all the time? My tanks are crystal clear with just sponge. If I need to clear something unusual I will take action, but adding a filter just because the pads are dirty seems overkill when (IMHO) they aren't really neccessary.

 

[Magnum Man]

the linked filters were some of the 1st filters I tried, when I got back onto tanks a few years ago... mostly because I used mostly Marineland Magnums previously... I hated those filters, as they require you to put them fully into the tank...the function was OK, except the diverter flap, was a weak link... but they were a huge eye sore... I like to hide any of the normal hardware, and there as just no hiding those... I have 2 that are in my old equipment tote....

 

[Rusty_Shackleford]

the linked filters were some of the 1st filters I tried, when I got back onto tanks a few years ago... mostly because I used mostly Marineland Magnums previously... I hated those filters, as they require you to put them fully into the tank...the function was OK, except the diverter flap, was a weak link... but they were a huge eye sore... I like to hide any of the normal hardware, and there as just no hiding those... I have 2 that are in my old equipment tote....

I agree it would be an eyesore permanently in the tank. I thought the OP was looking for a temporary or once in a while polisher.

 

[Sleeveless]

I probably wouldn't go through the expense of another Fluval, especially if you're looking for some to just polish the water.

I would do this. Run it for 24 hours once in a while to polish the water and then take it out till next time.

Amazon.com

a.co

The AC50 is $53 right now and I get 15% off with the Petco program I subscribe to so was just looking in that direction. Where the cost would get go up is the AC100 which is more expensive, but spec'ed for the tank size. If I don't need that high of a turnover due to the limited use of the secondary I'd go with the smaller. That Marineland filter looks pretty cool as well though.

 

[Sleeveless]

I agree it would be an eyesore permanently in the tank. I thought the OP was looking for a temporary or once in a while polisher.

I would run it 24/7. It would also help a dead zone I have on that side of the tank where some algae builds up (thats a whole different topic that is getting better though)

 

[FranciscoB]

A Word of advice. The AC filter (a nice small filter) may not fit the lip of the top of a regular 75g. An AC 70 would. Worth checking before buying.

 

[Sleeveless]

A Word of advice. The AC filter (a nice small filter) may not fit the lip of the top of a regular 75g. An AC 70 would. Worth checking before buying.

Good call. I do have a thick plastic trim on the Aqueon tank. Was even a little struggle getting the FX4 hangers over it.

 

[plebian]

You don't mention stocking, water changes, or feeding. The Fluval should be more than enough filtration for aquarium unless you're overstocking, overfeeding or feeding dirty foods, or slacking on water changes. Assuming you aren't doing any of those things, I would replace ALL of your filter media with 30 ppi foam. Proper biofiltration will provide all the "polishing" you need.

 

[GaryE]

I'm always in favour of more than one filter on a tank. It makes sense, probably because I'm an older aquarist and I've had enough filters wear out over the years. The old Marinelands seemed to fail in about 5 years, Chinese no names are good for 10 to 12 and Aquaclears have run for 19-20 here. But eventually, they all fail, and a second filter can be a key tool.

Polishing? To me, that's a matter of adequate water changes, careful feeding and sensible stocking. In that, I agree with @plebian . I never use pads or purigen - they aren't biological filtration products, and that and water movement are the whole goal of filtration to me. I have very clear water in my tanks (unless I add tannins) and clarity takes care of itself.

I'd look to the source of the lack of clarity you're concerned about. Substrate is often the culprit, followed by food choices and overfeeding.

 

[MaloK]

Your polishing filter could be rated to 1/4 of the output of the main filter and it would still be very effective. Even at 1 per hour turnover it would be enough.

The main reason for me to do the same would be the ease of maintenance, that is not to compare with the FX.

 

[plebian]

I'm always in favour of more than one filter on a tank.

I agree. It's a good idea to have a backup. In this case, the problem I see is that his current filter is already overkill with respect to water flow. This is one of the reasons I'm a UGF advocate. With any other system, excepting sumps, it's extremely difficult to house enough filter media for proper biofiltration without creating excessive water flow. The manufacturers are all obsessed with power ratings for marketing purposes.

 

[GaryE]

I have an FX 4 on my 120, and run it with an aquaclear 110, the larger HOB. I find that creates excellent flow, and fish in that tank have been thriving in the 3 years since I got the device. It's a small tetra and Cory tank, with fair planting. Depending on where the outflow is angled, I wouldn't consider that tank to be overfiltered at all. I'd use an FX-4 on my 75s, if I had one around. They are expensive filters.

But the polishing aspect is curious. The water should be very clear with that system. The use of polishing pads and such suggests something is off and we can't see what it is.

BTW - I have been making undergravel filters for some of my set ups, and they are old technology that works very well. I hadn't used one for 25 years or so, and became curious about resurrecting the idea for one of my set ups. I have several fish species that like shallow water, and a UG seemed ideal. I can report that it's great for that function.

 

[Sleeveless]

Maybe polishing was the incorrect term to use. I just use the fluval quick clear pads in conjunction with the chemipure blue. There are a couple things I was looking to accomplish with a smaller backup. I'll see if I can further explain:

1. Water is clear. FX4 is running with valve at 75% as I also have Angels and they are happy with the level of flow
2. I do have a dead spot due to high plants on the far side of the tank which I would use the secondary filter to help there as it tends to grow some algae (I'm also still working through a balance in the tank from some algae growth but it continues to get better as I slowly adjust except for the deadspot).
3. I have also had to treat my entire tank for illness in the past and using a second filter to add carbon to remove any added meds make it easier than pulling apart the FX4 to add to the bottom tray.
4. Overall backup in case of primary failure.

I do weekly 50% water changes. RO water used with Salty Shrimp gh/kh+ to remineralize with Seachem Fresh Trace. NiloG Thrive for fert and 1 root tab under my Amazon Swords as they are my only root based plants in regards to ferts. 0 Ammonia, 0 Nitrite, about 15 Nitrate.

Basically in relation to the secondary filter it is to cover a variety of smaller things (ease of maintenance too) so I think saying polishing may have been the wrong way to highlight my overall goal or idea.

To comment on the feeding replies, I still think my wife overfeeds and contributes to my algae issue. I've told her this and it's sometimes like talking to the wall. No health issues, but it creates an anomaly when trying to balance a tank to deal with that issue.