Gravel vacuuming

[ccurtis]

Ok party nerms, I have a questions in regards to gravel vacuumIng. I have a heavily planted tank with a heavy stock of community fish. My substrate is pea gravel. Plants seem to do fine in it as long as I use root tabs and easy green. 
 

I used to gravel vac every week with my water changes. I decided to run an experiment and not gravel vac for 3 months to see how things did. I did water changes only, and I monitored water quality and only had a minor increase in nitrates, but enough to make much of a difference. The plants flourished obviously, as they were getting more food (fish poop, left over food). The fish also seemed to be more healthy and active, and have began to breed more without gravel vacuuming as well. I just gravel vacuumed yesterday for the first time in 3 months. There was lot of gunk that came up. After gravel vacuuming, a lost a seemingly healthy fish the next day. He was old, no signs of illness, but was this just a coincidence, or was it because I removed a lot of mulm?
 

With that being said, what do you guys do? How often do you gravel vac? Or do you gravel vac your planted tanks?  There is a lot of back and forth on the internet about how often and the benefits of gravel vacuuming and not gravel vacuuming, but what are the nerms doing? 

[Fish Folk]

This is a very good question. I like the way you've framed it with your experience / experiment. 

 

Decomposition of organic material is comprehensive in natural environments. So, in theory, a normal build-up of mulm is an echo of nature. Plants flourish. But the "tree" of micro life is huge in a natural context, while in an aquarium it may be far less developed. Now, some things to consider: how much activity goes on in your substrate? For example, we moved a 20 gal tank today. Drained it all the way to within a quarter inch of the substrate surface. It was LOADED with Malaysian trumpet snails. It also housed some live black worms that managed to escape being eaten by fish awhile back. These large organisms are doing a lot of "lifting" in the system, converting and repurposing mulm while leaving behind their own separate waste. Smaller micro organisms are at work too. 

Water changing is probably the big difference between nature and our aquariums. This too is a double edged sword. Change out too much water . . . too frequently . . . and your tank gets jerked around with its chemistry. You mentioned an older fish dying -- that can _sometimes_ be triggered by just changing out a lot of water, and upsetting the chemistry, or changing water which has had some changes to it due to seasonal chemical additives, changes in amounts of dissolved gasses, etc. This is why the old aquarists always counseled you to "rest your water." Allowing water to rest (or stand with aeration) for 24-48 hrs can greatly balance the chemical dimensions of a water change. But few of us do this. We just suck out, and dump in.

Feeding is a factor to bear in mind. The less you feed (or skipping a feeding here and there . . . taking a day off feeding, etc) can help your bio filtration, plant absorption and nitrogen cycle all "catch up." Most of us feed too much at a time. I think that the more plants you have in your aquarium, the less you need to feed. 

To your questions directly: In general, we _lightly_ gravel vac 1x time for every 4x times we change water (25% - 50%). The goal is not to unsettle any anaerobic bacterial colonies, nor to clean up all mulm in the substrate column, but rather to lighten the load on the substrate bio that is processing so much uneaten food and waste. It also does something positive for the MTS in the substrate, helping them find new food to consume. 

[ccurtis]

Your response makes a lot of since. I do not have snails right now other than a few nerite snails. As far as other things living in the substrate, I’m sure there are the normal micro-organisms, but the only live food I feed is baby brine. Everything else is frozen, flake, or pellet. Honestly I don’t mind snails, just been lucky enough not to get them on my plants. I’m sure at some point they will come in. But trumpet snails would be a good addition to assist with things in the substrate. 
 

I do the pump and dump method of water changing, although yes, I agree if your water sets it’s more stable for sure. I also am definitely guilty of feeding more than I have too. I also agree the more plants you have the less you have to feed. 

[Will Billy]

1 hour ago, Fish Folk said:

To your questions directly: In general, we _lightly_ gravel vac 1x time for every 4x times we change water (25% - 50%). The goal is not to unsettle any anaerobic bacterial colonies, nor to clean up all mulm in the substrate column, but rather to lighten the load on the substrate bio that is processing so much uneaten food and waste. It also does something positive for the MTS in the substrate, helping them find new food to consume. 

@Fish Folk hit the nail on the head with that one. Not only do i try to not disturb anoxic and anaerobic bacteria deep in my substrate, i have a healthy population of detritus worms that i also try not to disrupt. 

[CT_]

Cool experiment!  I suspect if you kept it going for long enough your nitrate would settle to where it was before.  After all at equilibrium nitrogen in = nitrogen out.  It may be even lower at the end because plants have more opportunity to get some of that nitrogen in the solid waste (I count this as part of nitrogen out, so more out in plants means less out in water means less in water. ). 

Again this is at steady state, IDK how long it takes to reach steady state.