View Full Version : Why am I getting air bubbles in my substrate?
Jeremy S
01-02-2004, 7:01 PM
When ever I vacuum the gravel in my 75-gallon planted aquarium air bubbles come up with the dirt. They don’t smell at all and there seems to be more of them in the dirtier areas of the substrate. Is this something I should be worried about or are they harmless? Thanks.
Just a few quick questions to help establish an idea of what your situation is.
How much / how often do you feed? What fish are in your tank? and How often do you clean?
Ok, just checked your tank specs (maybe I should have looked there first? :o ) Georgeous tank by the way! I should be asking you for advice.
Your tank cleaning schedule is pretty good. If you keep your tank as trimmed as what I see in the pics, I don't think you have a vegetative rotting problem. Your bio load looks pretty full though so there may be excessive poop. So it leaves one question: how much and how often do you feed?
aquariumfishguy
01-02-2004, 8:40 PM
Sounds as if some gases might be getting trapped. And this could be due to the waste you have in this tank but after you answers Mataks q's we should be able to help you more. ;)
Or it may be only denitrification in the substrate - N2 is odorless, as is CO2 (another possibility).
Would the denitrification be caused from decaying waste?
Any undisturbed substrate of sufficient depth and appropriate particle size will have some denitrification, so a lot of planted tanks have such without it being noticed.
But to answer Matak's question, increased organic load - whether from original use of organics in the substrate or build-up of organics over time from feeding, plant debris, etc. - will definitely promote a steeper O2 gradient in the substrate, which in turn boosts the possibility/probability of gas bubbles. CO2 and N2 and harmless. With more severe anaerobic conditions from higher organic loads, real anoxia, you can get iron precipitation, H2S or methane generation. In undisturbed substrates even those are not dangerous (Diana Waldstad style tanks). This is because those gases are normally ozidized by bacteria before the reach the top of the substrate. If you disturb the substrate, and by this release them, they can cause problems. Very high organic substrates can also "leak" small amounts of toxic gases into the water column - this is classic dirty substrate issues with bottom dwellers, especially fish such as dwarf Cichlids and Corys which do some routine substrate low-level disturbance, being affected or killed first, schoolers and such only later.
HTH
I would guess then that a large buildup and/or release of any kind of gas is unlikely in a RFUGF, correct?
That depends on whether or not you always remember to vent the RFUG powerhead(s) after water changes. There just might be folk here who have been known to forget such basics - :shake: - do not ask how I am sure of this. But that gas is air, and not an issue unless it is blocking flow.
But you are correct - RFUG (so long as the prefilters are cleaned with any frequency) seems to me impervious to buildup, organic or otherwise, and the oxygenated water flow will negate any possibility of anaerobic or anoxic areas.
But hey, I'm prejudiced toward RFUG, I've been using it for Cichlids (the whole justification and need for my over-engineered RFUG) and BW puffers (as messy as Oscars, and need the buffering offered by coral/aragonite substrates, esp. with RFUG flow through that substrate). I'm even currently playing with Tom Barr's cast-off use of planted RFUG with pure water column fertilization.
http://www.aaquaria.com/aquasource/rtrrfug.shtml
Matak
01-03-2004, 10:24 PM
That's great news for me. Would removing the power head from the UGF plate tube achieve 'venting'?
It's good to see that not everybody is on the UFG bashing bandwagon. I do see their point in some issues, but I believe those issues can be satisfactorily dealt with.
BTW Jeremy, my apologies for semi hijacking this thread. I hope it is still of some use to you.
Yup, lifting off the head and turning it on its side or upside down to release the trapped air should do the job.
Mine are all Penguins with the reverse flow kits, which have a rubber stopper at the high point of the flow path, so I just have to remember to remove the stoppers to vent air and replace them before I turn the pumps on again.
Those setups BTW are easy and work well for me. For such an inexpensive pump they are remarkably lasting. I have not used anything else for RFUG since they came on the market. I think they suggest the smaller pump (650?) for RFUG, but I use the 1140 on many (most) setups. If you ever do more, at least look into them. The prefilters are a bit coarse, but with weekly rinsing it has not been a problem for me. My prior DIY setups were a PITA.
I was quite fortunate with my DIY setup. I found tubing pieces at my local hardware store that made a good and quick link between my power sponge pump and the inlet tube of the UGF plate. It only takes a couple of minutes to disconect, clean and reconnect the apparatus.
RTR, you said:
I think they suggest the smaller pump (650?) for RFUG, but I use the 1140 on many (most) setups. Are you quoting litres per hour? If so, I may be grossly under powered. Just checked mine and it is rated at 200 L/Hr. My plate is 12" X 12". Do you recomend that I step up to a higher volume pump? BTW, here is what I use as a pump (http://www.hagen.com/canada/english/aquatic/product.cfm?CAT=1&SUBCAT=107&PROD_ID=01001600011001).
No, those are Penguin model numbers of their powerheads which match up to their reverse flow kit. I don't have a 650 still boxed, so can't give a rated output on that model without a web search, but the 1140 is rated at 300 US gallons per hour (or about 1140 liters per hour, so maybe the 650 is nominal liters per hour). I use that on 12x24" plates, 18x18" plates, or 12x30" plates - so from just under 300 square inches to ~360 square inches. Those are all with over-engineered RFUG, giving the plate plus one or two layers of bonded polyester, a layer of fiberglass screen, the eggcrate (no significant flow resistance there) plus 1-4" of gravel - so I am operating high-resistance systems. For plates smaller than those, I use the model 650.
Whether or not you are underpowered depends on how much area you are driving, the fineness of the prefilter, and the depth of your substrate. From the data above, my driving would be at a rated (but actually much lower) flow of about 1 gallon per square inch per hour (or ~3.8 liters per hour). Remember that pump ratings are zero head, and I operate high-resistance systems. If I actually get 20% of rated I would be shocked, but it has been too long since I did that development work - I have vague memories of maybe 15-20% of rated flow with a meter bridged in line (and don't bet the farm on >10 year year old memories), and that would have been with the shallow substrate.
HTH
Matak
01-04-2004, 10:37 PM
Well RTR, I won't bet the farm, but I'll sure use those ballpark figures as a guideline. I'll figure that being within 50% of your figures is acceptable but if there is a greater than 50% difference, I'll look into a differently powered filter.
I'd like to thank you for taking the time to answer my questions. :)
My pleasure - and associated apologies to Jeremy S whose thread we hijacked - as I hate to see UG/RFUG given a bad rap because folks do not understand how and why they work or what they need to work well.