TANK OF DEATH......

OnlyGenusCaps

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Plants help for sure, their tanks are sparsely (if at all) planted...the LFS does WC's weekly, but you're not going to get the trAte-harboring gunk out of filters w/out cleaning them
Well, I guess I don't know how to explain it then. Maybe I'm better at gravel vacuuming than I realize. ?

All I know is it worked for me for years. Well enough, I'll likely give it a go again if the situation arises.
 

Colin_T

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Didn't know you could still even buy under gravel filters!? Can you grow live plants ok with those? Wouldn't they all need uprooting if you needed to clean the filter?
Undergravel (U/G) filters are still available, it's just most shops prefer to sell power filters because they make more money from them and people think they are better than U/G filters.

Plants get left where they are and you simply gravel clean around them. Leave an inch or so of undisturbed gravel around the plants so you don't damage their roots and gravel clean the rest of the substrate.

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UGFs are outdated, and hard to maintain, much better options out there...
To maintain an undergravel filter you simply gravel clean the substrate every week when you do a water change. Easier than a power filter.

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The biggest problem with them is that you have to wreck the substrate to get them out and clean them, they become nitrAte factories...
No you don't have to remove them to clean them. Gravel cleaning removes the gunk in the gravel and from underneath the plates. They do not become nitrate factories. The reason nitrates go up is because of fish, fish food and lack of water changes.

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My LFS (old mom-and-pop store) uses them in all of their tanks, and rarely cleans them...tested a recent sample of their water, 0 ammonia, 0 nitrItes, 180+ nitrAtes
Are you sure it wasn't a faulty test?
Maybe the tank had a lot of fish in, maybe they had fed the fish a lot of food, maybe they were due for a water change that day. Maybe there was a nitrite reading as well but it didn't show up on the test. Nitrate test kits read nitrite as nitrate and give you a false reading.

They might have not done a water change for a while, but it isn't undergravel filters that cause nitrates.

I ran undergravel filters on most of my tanks, including plant tanks, and gravel cleaned them each week when I did the normal weekly water change. I had tanks running for over 15 years with the same U/G filter and never had a problem with nitrates. I fed my fish a lot, and did big water changes and gravel cleaned the substrate each week. My nitrates were always under 20ppm even at the end of the week.
 

Slaphppy7

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Thanks Colin, informative, I'd like to research more.
Busy night here, I'll get back to you soon as I can, did not mean to go off-topic on the OP's thread, apologies in advance.
 

StevenF

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The biggest problem I see with under gravel filters is that most use air stones in a tube to move the water through the gravel. With such a setup you might get a little more than one gallon of water flow through the gravel per day. At such a low flow organics will build up in the gravel. There is simply not enough water flow for them to work well and eventually the the buildup of organics will stop the water flow and the filter will not work effectively.

I read a post some time ago of a person that decided to replace the sir stone with a pump and was able to do it without tarring down the tank. It took days for the pump to pull up clean clear water from the filter. Other people have reversed the flow of water from down thought the gravel to up though the gravel. This revered flow can lift organics to the surface where they would be easier to remove with a water change and gravel vac.

One advantage is the they make it easier for plants to get the nutrients they need to grow. In sand substrates there is not a lot of water flow though the sand. As a results the substrate will slow plant growth. Many people therefore use root tabs to feed the plants. but it is difficult to know when the tabs need replacement. I prefer a liquid fertilizer since it gets everywhere. Even into sand substrates. Although the plants definitely do better in a more porous substrate like regular acquiring gravel.

With under gravel filters with mechanical pump nutrient levels in throughout the substrate will stay uniform and plant growth can be faster. And you just fertilize after every water change.
 

Fishiemang

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.....I currently run a UGF in my 30 gallon. Ain't had any issues in there at all. I can see under the tank, and I ain't vac'd that thing in 3 years. Is a small amount of debris under there at any given time, but there are a LOT of roots from the plants so...it mostly gets sucked up and blown into the tank where the Emperor 400 mechanically cleans that out. They are excellent for biofiltration, no nitrate spikes.

I also only feed that tank every 3 days so...there ain't much crud buildup. I did notice that my TDS in that tank is well over 1000 so ima do the first in a.series of small.water changes starting tomorrow. Bring that down. My tap is 140. Plus, couldn't hurt too much to get some.fresh water in there. The fish may like it...I dunno. I don't speak blub blub....
 

Colin_T

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The biggest problem I see with under gravel filters is that most use air stones in a tube to move the water through the gravel. With such a setup you might get a little more than one gallon of water flow through the gravel per day. At such a low flow organics will build up in the gravel. There is simply not enough water flow for them to work well and eventually the the buildup of organics will stop the water flow and the filter will not work effectively.
You get a lot more than a gallon a day if you have a good undergravel filter with a decent airpump. It's obviously not as much as a power filter or using a powerhead on the uplift tube, but does the job.

Because you have 2-3 inches of gravel over the filter plates, it prevents dead pockets and anaerobic areas from forming. Even with 4 inches of gravel they still don't go anaerobic because they have water moving above and below the gravel, as well as through it.

The huge surface area provided by the gravel holds massive amounts of good bacteria that keep the ammonia and nitrite levels down.

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I read a post some time ago of a person that decided to replace the air stone with a pump and was able to do it without tarring down the tank. It took days for the pump to pull up clean clear water from the filter.
That is caused by a poor gravel cleaning technique. If you have an undergravel filter in the tank, you start the gravel cleaner syphoning and then push the gravel cleaner into the gravel. Push it down until it touches the filter plate and leave it there until the water being sucked up is clear. Then lift the gravel cleaner and move it to another area. This sucks the gunk out of the gravel and from underneath the filter plates.
 

madmark285

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The biggest problem I see with under gravel filters is that most use air stones in a tube to move the water through the gravel. With such a setup you might get a little more than one gallon of water flow through the gravel per day. At such a low flow organics will build up in the gravel.

Which raises another question: What is the optimum flow rate of water thru the biological media?

I have a sump filter with a Lifeguard Model 3000 pump, estimated flow rate at ~500 gph. The flow rate is so high, my fish could go white water rafting in my sump :rolleyes: Does the bacteria have enough time to convert the ammonia and nitrites going thru the filter beds? Speculation but I would say no, it may take multiple passes thru the filter to remove the ammonia and nitrites.

On the other hand, the slower flow with under gravel filters may be closer to that optimum flow. If your gravel bed can remove all the ammonia and nitrites in one pass, why do you need a higher flow rate?
 

madmark285

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The biggest problem with them is that you have to wreck the substrate to get them out and clean them, they become nitrAte factories...

I hear the term nitrate factories in the reefing forums. As one experience reefer said, this is a misnomer as that is what you want with a biological filter, complete the nitrogen cycle which converts organic material to nitrates. If you don't want a nitrate factory, use a protein skimmer which removes the organic material before it breaks down into ammonia.

Without proper cleaning, wouldn't all gravel beds would become a nitrate factory?
 

madmark285

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They worked great! With some basic maintenance they functioned exceptionally well for years. Worked really well actually, as I think about the successes I had!

Here is an interesting read about undergravel filter, The Under Gravel Filter Controversy. The rather ugly but effective internal sponge filter seems to have replaced the undergravel filter.

Here is an idea I had, make a large overflow with multiple thru hull fitting with suction screens/caps. Fill the overflow box with gravel and grow emersed plants in it. Now you have a large biofilter and the roots system are well oxygenated.
 

OnlyGenusCaps

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Thanks for the link. Interesting read!
Here is an idea I had, make a large overflow with multiple thru hull fitting with suction screens/caps. Fill the overflow box with gravel and grow emersed plants in it. Now you have a large biofilter and the roots system are well oxygenated.
Something tells me that if you aren't familiar with his videos I should introduce you to the Fishman. The one I just linked talks about two types of gravel filters he's built, one that seems a bit like the rig you just described. In general, I like his videos, though I am glad he has changed the intro music (sorry the linked one has the old intro music). He isn't a talking head into the camera. Builds stuff that's interesting. Does experiments to test claims, particularly in filtration (though I'm more cautious than he is when making claims of allelopathy). All in all, I think he's a decent resource, and one of the better folks on YouTube. I'd be curious about your take though.
 

madmark285

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Something tells me that if you aren't familiar with his videos I should introduce you to the Fishman.

Thanks so much, a mad DIY'er! I watched a couple of his video. He is great, very creative. I like his polishing filter, I may make one of those using PVC pipe.

Below is my fish room, the dead space in the corner would be a perfect place for some type of gravel bed filter.

Fish Room.jpg
 

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