# Hang On Back Filter Modifications - Media



## jarvitron (Aug 6, 2012)

Gravel is kind of low surface area ratio, you could use some lava rock which would have a lot of good surface area for bacteria to colonize, or some LECA and put plants in it (there are a lot of great pictures of planted hob filters on this site). I just poured in some canister filter "ceramic rings" and strung two pieces of bacopa up into them, not really dramatic or anything but that plus a little pothos leaf jutsu obscures my hob output pretty nicely.


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## pejerrey (Dec 5, 2011)

Check out "planted hob thread"


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## gus6464 (Dec 19, 2011)

All I run in my HOBs is some form of bio like Matrix and Purigen. It's really all you need. Ohh and some filter floss.


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## AirstoND (Jun 17, 2011)

charcoal has more surface area or pores that bacteria are able to attached themselves to and get to practice their mojo in reducing ammonia and nitrates for tank health.

Someone else also mentioned putting plants, as their fine hairy cellulose roots work in a similar way.

Solid rocks are typically heavier (with the exception of pumice or lava rock) and are denser than coal and plant/plant roots, so they reduce how much water is being effectively "cycled" through tank


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## Diana (Jan 14, 2010)

You can stuff the HOB with whatever you want, but the points made above are all good:

Heavy stuff like river rock/gravel adds to the weight hanging from the tank without adding much benefit. 
I have used 3/8" lava rock for several of the reasons stated above. Activated carbon will do the same. It does not release whatever it has trapped, but becomes a home for beneficial organisms, including plants. 

You can plant the HOB with no media for the roots. Use hanging plants, though. Upright plants will not stay upright without some support. 

The stringy, gooey stuff is not nitrifying bacteria. It is more likely an algae. Nitrifying bacteria grows in a film that is stuck to surfaces. It can build up several millimeters in thickness, but never grows in long strings. You can safely clean up that gunk and not have any effect on the nitrogen cycle. 

Nitrifying bacteria will grow on many surfaces, but does need high surface area and good water flow. Ceramic bio media, lava rock, sponges, floss and many other things are good.


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## crcarlsontech (Jul 10, 2012)

Damn! Thanks everyone for the very informative replies. 

Looks like I am off to see what kinda plants I want to put in this HOB. My 20 gallon long has no cover so I feel that a plant in the hob would suit it well.


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## Diana (Jan 14, 2010)

Golden Pothos, Heartleaf Philodendron are 2 low light house plants that do well growing out of an aquarium or filter. 
The Philodendron is slower, better behaved. The Golden Pothos grows so well it made several laps around my living room. 
I have Syngonium in another tank (72 gallon), near a window. This one is really large, I do not know if it would stay well behaved enough for a smaller tank.


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## kiera (Jul 10, 2011)

How do you plant a HOB? And what are the benefits? I have a HOB with one stage of charcoal filtration that I have no desire to use, and I also have a devil's ivy that could possibly be used to restrain Godzilla if you could get him to stand still.


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## Monster Fish (Mar 15, 2011)

You can reduce your nitrates naturally with plants in your HOB. Also it looks nice.


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## mistahoo (Apr 25, 2012)

I normally run my HOBs as strictly mechanical. I remove the filter cartridge and place a coarse sponge in and then place a mesh bag of ceramic rings on top of the sponge. Then the 'topping' magic beans (Purigen)! This usually keeps my tanks really clear. If you want to run bio media in your HOB, I wouldn't recommend lava rock unless it's in small pieces. I'd recommend stuffing a lot of matrix or Eheim ehfisubstrat Pro in a bag. Both have a lot of surface area for bb to grow on and very great for big bio loads. Both are much easier than having to deal with plants getting enough light or being able to stay put in the HOB, etc.


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## Diana (Jan 14, 2010)

Plants that grow with their leaves in the air can get all the CO2 they need no matter what is going on in the water. These plants are better nitrogen removers than plants that need to get their CO2 from the water. 

House plants are almost always tropical plants that grow in rain forests, so are well adapted to damp roots as long as there is a reasonable oxygen level. Growing them in the filter or in the tank allows the moving water to bring them the nutrients they need (fish waste) and keeps the water well oxygenated, so they do really well. 
You will need to be sure the plants growing out of the tank get enough light. I grow mine near a window, but you could also put a spotlight on them with a plant specific light. 

Plants that grow vertically will need something to support their roots, because it is the roots that keep these plants upright. I tried growing vertical plants with just some ties and they really did not thrive. When I planted the same species in a lava rock planter with aquarium water piped through it those plants took off and grew really well. 
Hanging plants seem to do better in an aquarium or filter, roots in the water, stems and leaves in the air. If you can attach the plants to the wall (nails, cup hooks) they will really take off and do well.


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## California (Sep 13, 2012)

I'm assuming your goal is to keep bacteria alive, and that you're not concerned about water clarity/debris. So, just get a filter media bag and fill it with biomax. Insert it into your filter and remove the carbon if you wish.


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## Diana (Jan 14, 2010)

In a planted tank the plants are so much of the bio filter that there is not such a pressing need to have so much bio media for bacteria. There are plenty of lodging sites on all the surfaces of the tank such as rocks, driftwood, plant leaves, substrate (upper, high oxygen areas) and so on. 

Removing the normal media from the filter (sponge, ceramic noodles) and using that volume to grow an emersed plant is a good trade off in terms of nitrogen removal, but not so great for the debris removal. 

The plants (house plants) do not need to be in the filter itself, you can keep sponge, floss etc. in the filter. The plants can simply hang in the tank, Roots in the water, stems and leaves in the air. Some roots can get quite massive, though.


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