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stephanieleah 02-07-2010 01:16 PM

gravel vac and water chemistry
when I go crazy with the gravel vac during my water changes, sucking up debris that has gone under the top layer of gravel (it feels good to watch all that "dirt" go up the hose), am I affecting my water chemistry? I imagine that under the gravel there is a different chemistry with nutrients, aerobic bacteria, detritus broken down by shrimp and bacteria, oxygen and carbon dioxide, and when I bring it to the surface with a vac it might mix into the main tank water and alter the water chemistry. comments?

i'm posting this in the plants section because i'm mainly curious about planted tanks...ever since it's been suggested to do gravel vacs by simply sweeping the vaccuum lightly over the gravel during wc.

cmc29 02-07-2010 01:25 PM

I wondered that myself when i set up my planted tank, because before i would always dig deep and get lots of dirtbefore i went to the planted set-up. But, when i decided to go planted i used a layer of sand over my flourite (to protect myself from my own obsessiveness about cleaning my tank). It has helped me "resist the urge." , since i don't want to stir up too much sand.

Byron 02-07-2010 08:21 PM

I believe the more important issue is that you are depriving your plants of needed nutrients by removing the detritus and mulm that builds up in the substrate. Some never vacuum the substrate in planted tanks. I only run the Python over the top (not really disturbing the gravel) where it is open (no plants) and down into the gravel along the front where I feed my bottom fish, to keep the substrate clean. There is a school of thought that barbel degeneration in catfish is due to nitrates; some eminent ichthyologists hold this view, so I won't argue contrary.

But back to the substrate, there is a complex array of aerobic (and some anaerobic) bacteria living in the substrate, and they work in connection with the plants to break down detritus and the plant roots assimilate the nutrients. Along with oxygen in the water that passes through the substrate, plant roots release oxygen to keep those aerobic bacteria alive. A substrate without any organic matter is only an anchor for plant roots; some use enriched substrates (you may have done this, I've forgotten) to ensure an organic mix, but a lot of it comes from the fish waste and bacteria processes.

As for releasing this detritus into the water, it is in the water when it is in the substrate, or in the filter media; nothing changes, bacteria convert it to organic nutrients. But it is better to have this occurring in the substrate so at least the plants can benefit from it.


stephanieleah 02-07-2010 09:44 PM

Noted. Water chemistry isn't the issue then. But I have one question on the note of cleanliness...

Don't your bottom feeders stir up stuff from under the gravel (I have three very active foragers and a pleco that whips his tail and stirs up crumbles all the time) and do you just let that stuff settle back down?

Sorry to post something so similar to my last thread about gravel vacuuming but I have to believe in the system before implementing it.

Angel079 02-07-2010 09:54 PM

There's 2 factor's I'd consider here that are important IMO:
1) Plants
2) Shrimp

I know some of this will sound repetitive to you thinking back to your "spotless tank cleaning" thread a while ago.

What you're referring to as dirt getting sucked up is actually what you'd compare to in the gardening word (outdoors that is) as manure. Much like the outdoors gardening world this is very beneficial for your plants.
As most you know by now all my old tanks never gotten liquid ferts or the sticks etc up until I now stared this fert matter in my 55g....So why did these other tank's plants still thrive?
I belive it was the simple combo of my stock; source water and me letting mulm built up. Which initially started simply because I couldn't get inbetween the plants and then in comparison when I built my 55g Yellow tank noticed that my plants in the "dirt" tank were thriving much better then the exact same plant (same mother plants and all own raised by me, so not a store difference there to consider) in the super clean Yellow tank (where I could get inbetween to vacuum).

Nowadays I have 2 spots I gravel vac neatly and the rest is left alone: That is for one the very front glass which for visual reasons and not having plants right up to it I vacuum and the 2nd spot is lil areas I try to keep plant free to feed cory's at.

Now the second part here; and that's the more important part IMO are your shrimp.
Your plants will still thrive because you use all sorts ferts there...The shrimp live off of that mulm built up and there's certain nutrition added to their diet this way (eating what you'd refer to as dirt) that is actually know to help prevent molting issues (just like bog or oak leaf's would).
So while your plants have a secondary source so to say; for the health of your shrimp I'd advise let it built up in the back of the tank at least so they have a snack bar with healthy foods there!

Edit: Upsy...that became kinda long story there didn't it...I'm sorry :-(

Mean Harri 02-07-2010 10:02 PM

I'll go out on a limb here. Mostly because I like the adrenaline rush of living dangerously. Meaning I may be wrong. Likely I am, but idc.
There are likely some particles that settle into the gravel that are not fully disturbed and stirred up by bottom dwellers. The stuff that is will continue moving around. What gets sucked out by just passing over the surface w/ the gravel tube will lessen the load in the tank, or maintain a healthy load with regular wc's. What gets in behind and under plants will be broken down by bacteria and consumed by plants. I guess what I mean is, as long as it is not left to become filthy it should be fine to just lightly skim the surface in open areas.

TL:DR (too long didn't read) What Byron said.

Mean Harri 02-07-2010 10:30 PM

In regards to my above post. TL;DR I didn't mean Byron's post was too long. I meant if mine was too long to see Byron's as I agree with his. In other words, if you don't wanna finish mine... you know what I mean.

Sorry Byron. It doesn't read how I meant it.

stephanieleah 02-07-2010 11:09 PM

@ Eric: got it. That's what I wanted to confirm. No post is too long for me LOL. You're talking to Ms. Long-Winded.

@ Natalie: Yes! Shrimp snack bar. And they do accumulate in the most un-vacuumable areas (esp Java Fern roots and java moss).

Oh, and Eric one thing Byron mentioned was that he vacuums around the areas where the corys eat because the barbels tend to be affected (negatively) by nitrate, and accumulation of debris = no good for the barbels. Which is a concern since I have yo-yo's whose barbels have been looking on the pinkish side lately. Could be due to sexual maturation from what I've read.

SO Natalie one more thing...when your bottom feeds forage around (do you have any rambunctious ones in there?) don't they mix up mulm and if so what do you do about it? Just let it whirl around in the tank? That's the issue I have, I feel like it mixes in the water and creates a higher concentration of dissolved matter in the water. I just get this feeling (could be totally OFF) that it deteriorates the quality of the water when stuff gets stirred up into the interior of the tank (meaning, floating all around the tank and not just the bottom). Yeah, it settles, but then more just gets mixed up again. What the heck?

Angel079 02-08-2010 10:50 AM

Rambunctious... You mean like when I got the Bronze Cory's introduced to the 55g and found ALL my dwarf baby tear half floating the next AM???
They stir up stuff in the back yea but what floats through the water get's sucked in by the filter intake anyway; the new one's now are too young to have a decent mulm built up; but like my old one's before the move I can actually say that somewhere between shrimps and a bunch cory's there was never a situation that the mlm had built up several inches or anything like that; somewhere between breaking down and all them guys snacking it kept it 'clean'. As for the readings on the old established tanks (I'll leave the new one's out of this cause well they're new lol) I never had any elevated NO levels; can't find my old chart right this sec but the NO3's in the tanks back then always stayed pretty low (like 5-15mg/l low).

Byron 02-08-2010 02:11 PM

I never really notice stuff being churned up by the corys; maybe it is very minute and I just don't see it. Stephanie, do you mean seeing large bits of stuff? Even when I vacuum deep along the front, it is very fine particles that come up. Partly due perhaps to fish, I remember when I had some larger plecos there would be much more noticeable mulm than with my smaller fish. Livebearers for instance produce more visible waste (in size) than characins.

One further point in relation to this, on water changes. It is commonly held by a majority of natural planted tank aquarists that water changes are not necessary and should not be performed regularly if at all. I have not embraced this thinking...yet; but it is held by Diana Walstad and Tom Barr, both highly respected experienced aquarists with professional training in biology and microbiology. Mr. Barr has a BSc in aquatic biology, a MSc in Botany, and is currently pursuing a PhD in Plant Sciences. I have had some very rewarding and informative discussions with him. If one does no water changes, one is obviously not vacuuming anything from the substrate.

Nature is indeed amazing, if we only let her get on with it.


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