20 Gallon Stream Tank with an HMF and an Undergravel Cave!

Hey guys, here's another build! I wanted to make a new home for my Stonecat, as he has outgrown his 10 gallon, so I decided to use a spare 20 gallon long to construct the perfect Stonecat habitat. I knew I wanted to do an HMF (Hamburg MattenFilter) to help hide the equipment, as this is going to be a display tank, actually located underneath my 75 gallon turtle tank (If you haven't seen that thread, check it out here: http://forum.nanfa.o...080#entry106080 ) I started by cutting part of the background I had had on the tank off to allow room for the HMF. Then I siliconed that to the exposed wall, tilting it sideways, as it wouldn't need to cover the bottom are because that would be covered with substrate. I also painted the back and sides black and siliconed in a short glass divider to hold back the substrate by the HMF. Sadly, I don't have any pictures of this before it was filled up. However, I do have pictures of the plumbing I did for this tank. I'll start with a picture that will show it all together:

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I'll start by zooming in to the cave so you can see what I did to prevent it from becoming stagnant:

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Above you'll see an endcap with holes in it inserted into the endcap of the back of the cave. This allows just a slight amount of flow to get through into the cave, keeping out debris and making sure the water keeps moving. Here's a look into the mouth of the cave:

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Now, moving over to the other output of the pump I have a spraybar, with a hole in the corner included to put some airline tubing through so I can get some nice bubbles going:

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Here's a picture of the whole system with the filter pad on it:

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Finally, here's a picture of how it sits today. It's still cycling, which is why I have the bags of carbon in there, both to help clear it up and to keep down the smell from the piece of shrimp I'm using to cycle it. There's also a picture that gives a look into the pump chamber:

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Thanks for reading! As always, I'm up for any and all questions! But also, I have one question for you; how do you think Mottled Sculpins would fair with the Stonecat? I would love to keep them together in this tank, as they are the stream fish that don't really work in the usual community setting.

Very cool...can't answer about the sculpins

Thanks! I had the idea the other day and fell in love, so I'm really glad I got it together!

Being a novice, I'm not familiar with the "HMF" filter...from the pics it looks like an oversize sponge filter hidden behind a 3D setup...is this accurate ? I'm always interested in technical details and different setups...thanks

Rich

Yeah, you're pretty much there. It's like a wall of sponge, at least 2 inches thick, that works similarly to a sponge filter, yet much bigger. You only have to clean 1 to 2 times a year, depending on stocking levels. It's pretty amazing.

You only have to clean 1 to 2 times a year, depending on stocking levels.

The end product of any bacterial filter is nitrate. Bacteria convert ammonia to nitrite to nitrate. Increasing the surface area for the bacteria to colonize does not change their end product. No bacterial filter, regardless of how good it is at housing the bacteria, can decrease the frequency of nitrate induced water changes. All bacteria filters do is decrease the frequency of ammonia induced water changes.

There are two reasons to do water changes: if ammonia is above 0 ppm ( no, 1ppm ammonia is not okay) or if nitrate is above the threshold tolerable by the species. For most fish the nitrate toxicity threshold is 30 ppm, although bluegill are far more tolerant than, say, discus. By converting the ammonia (which is toxic at 1 part per million) into nitrate (which is toxic at 30 ppm), bacterial filtration decreases the need for water changes by thirty fold. All of the standard filter designs (waterfall, canister, sponge, HMF, fluidized bed) are capable of converting the ammonia to nitrate as rapidly as the ammonia is generated. Which filter you use really doesn't matter as long as you don't have ammonia present.

There are only three ways to remove nitrate from an aquarium:
1. water changes, which dilute it
2. plants, which eat it. See table 2 of http://www.theaquari...ical_Filtration to see how many hours it takes them
3. anaerobic nitrifying (N2 gas producing) bacteria, which are mostly not present in your average aquarium. Deep sand beds, maybe.

Methods 2 and 3 decrease the frequency of method 1.

Edited by EricaWieser, 10 April 2013 - 02:34 PM.

I like !...must make for a nice clean setup...

I never said I wouldn't change the water, I was referencing rinsing the filter itself. I also have a fairly deep sand bed, and plants.

And yes it does! I'm very pleased with it!

Actually fine-textured biofilter media (like foam or sand) CAN achieve pretty good denitrification of nitrate to N2 gas, after it has gotten some age and "filterschmutzes" (organic debris + microorganisms) that create local patches of reduced flow rates and low oxygen. That's an important part of the mattenfilter concept -- the large area allows you to run it undisturbed for many months or years (depending on fish load) and let those semi-clogged areas develop where the anaerobes can do their work. (it makes a great blackworm condo too).

No bacterial filter, regardless of how good it is at housing the bacteria, can decrease the frequency of nitrate ...
... anaerobic (DE-)nitrifying (N2 gas producing) bacteria, which are mostly not present in your average aquarium. Deep sand beds, maybe.

Yeah, I was actually just going to post something about that. I really don't know why there aren't many people who use this filter!

Actually fine-textured biofilter media (like foam or sand) CAN achieve pretty good denitrification of nitrate to N2 gas, after it has gotten some age and "filterschmutzes" (organic debris + microorganisms) that create local patches of reduced flow rates and low oxygen. That's an important part of the mattenfilter concept -- the large area allows you to run it undisturbed for many months or years (depending on fish load) and let those semi-clogged areas develop where the anaerobes can do their work. (it makes a great blackworm condo too).

Interesting.

I love the vented cave! What plants do you have in there?

I had been considering the mattenfilter as well, at least for my smaller tanks that I run off sponge filters. More filtration off the same air pump, so to speak. I saw a modified one where a hang on the back style filter was used instead of a traditional air lift tube. Do you have any thoughts on how well this would work on a large tank like a 75 gallon? I assume that I would have to channel the outflow to the other side of the filter somehow.