Brown water - gravel vac

[BAT]

Nerms,

I just gravel vac’d an established tank and the water was brown. What is that brown dust in the water when you gravel vac? Where does it come from?

[Guppysnail]

Fish poo, leftover food decayed leaves all break down to the brown “dust” in the gravel. Most folks call it mulm…I think because it sounds better than fish poo 😁

[Scott Stevenson]

I assume that when you say the water is brown you mean the water that ran into your bucket from the gravel vacing, not the actual water column of your tank. One of the reasons to have gravel in your tank is to hold down all the fish waste, uneaten fish food and potentially any decaying plant matter. really any detritus that finds it's way into your tank. When you grav vac you are pulling all that matter out of the gravel and out of your tank. It's why you grav vac. That's why ppl might distinguish between, purely water changing and gravel vacing.

Additionally, all of that "brown stuff" decays and releases more ammonia, also heterotropic bacteria will feed off of it and release additional ammonia.

I hope that's helpful. 

[BAT]

Very helpful @Guppysnail. @Scott Stevenson thanks!

is this why the water smelled a bit odiferous ? Like a sulfur smell?

@Scott Stevensoncan you explain why the heterotrophic bacteria convert it to ammonia and not nitrite?

[Guppysnail]

There are a few reasons for suffer smell. Most common is less oxygen in the substrate and when you vac you suck out the gasses released by bacteria breaking down the detritus.  Also conditioners like prime and safe are sulfur based. 

[Torrey]

Guppysnail & Scott Stevenson answered most of your questions.

Heterotropic bacteria is different than nitrifying bacteria, which is different from denitrifying bacteria. 

Bacteria is generally named for its shape or its function. Think about E. coli: it's naturally occurring in the colon to help our GI tract extract nutrients. Don't want it in the blood stream, it can be lethal.

Beneficial bacteria in the aquarium facilitates the breakdown of waste into bioavailable food for plants. Deep substrates can grow a hydrogen sulfide compound by breaking nitrogen down. If you disturb a pocket of the gas, it smells strongly of sulfur.

If you use bottled bacteria, some of the bottled bacteria available will have a slight sulfur smell. 

If you use Prime, you will notice a sulfur smell.

As for why the heterotropic bacteria will produce ammonia instead of breaking ammonia down into nitrogen, imagine asking a firefighter trained for hotshot work against forest fires to perform brain surgery. 

Both brain surgeons and fire fighters are humans, but can both humans do exactly the same job if they specialize in different job trainings?

[Scott Stevenson]

In my limited experience, I've never noticed a sulfer smell when doing water changes/grav vacing. It usually smells like not overly offensive lake water...to me anyway.

As far as the bacteria go; That's what Heterotropic bacteria does. It lives off of organic matter and it's waste is ammonia. Ammonia is only converted to nitrites by Autotropic (beneficial) bacteria. The Nitrites are then in turn converted to Nitrates, again by beneficial bacteria (BB). The Nitrates can then be used by live plants or algae as fertilizer. All of that together is called the Nitrogen cycle. That's what "an established tank" means. Ppl refer to this as a cycled tank. 

If this is not happening in the tank, than it's not really "established"...again I hope this helps

Edited February 12, 2022 by Scott Stevenson

[BAT]

If the heterotropic bacteria are part of the cycle and their ammonia products can be decomposed by the autotrophs then why do we need to do gravel vacs? 

[Guppysnail]

It is more than just the ammonia released. There is a lot of solids “brown dust” and stuff the bacteria does not consume. If you had an active substrate or organic soil and more detritus critters that live in those substrates to consume what’s left the need for gravel vac goes away. In inert gravel with not enough of the correct fauna it just builds up and releases excess nutrients into the water. Also it’s poo and bad stuff grows in it as well if not consumed. Hope that very non sciencey explanation helps. I’m sure the science folks on here can explain it in better terms for you. 

[Scott Stevenson]

In addition to what Guppysnail has said, The process isn't necessarily always 100 percent efficient. and as I said before the waste laying around is just going to continue to decay into additional ammonia. also if the mulm is just allowed to build and build those gas pockets that were talked about could eventually be dangerous to your fish. Likewise in large amounts it will eventually overwhelm your gravel, making your water column full of debris and taxing your mechanical and even your biological filtration/nitrogen cycle and possibly sparking run away algae growth.

Heterotropic bacteria is necessary for the process, but if you give it too much fuel it can get out of hand. Heterotropic bacteria seems to multiply much faster than Autotropic, meaning that if there is abundant food sources for the HB it can potentially multiply out of control causing a bacteria bloom, making your water column a cloudy, milky color. The AB will not be able to catch up any time soon and your ammonia will spike. Ammonia spike equals dead fish.

There is a phenomenon known as "old tank syndrome". After a tank is cycling well for many many months it is sometimes called "well seasoned", this is a good thing. it allows the natural ecosystem that you created to do much of the work (in the best case).If there are live plants and algae is kept in reasonable check you can potentially go longer periods between water changes and gravel vaccing, however what tends to happen is that as you go longer and longer between water changes/gravel vaccing, those ammonia and Nitrite and nitrate levels will start to creep up, if you're not keeping an eye on your water parameters. you're long time fish can adapt to this SOMEWHAT but it is not really good for them and even then it will eventually be lethal to them. Additionally, adding new fish that are not accustomed to the water parameters of an old tank usually die.

regular water changes and gravel vaccing can help keep this from happening. 

[BAT]

Thanks @Scott Stevenson

this explains what happened when I had an out of control spike 6 mos after starting my tank. Then our betta got fin rot. So now that he is healed I am making sure the tank is totally stable before he returns. 

[Torrey]

On 2/12/2022 at 10:15 AM, BAT said:

Thanks @Scott Stevenson

this explains what happened when I had an out of control spike 6 mos after starting my tank. Then our betta got fin rot. So now that he is healed I am making sure the tank is totally stable before he returns. 

That is good that you are getting things stable before returning the betta.

If you want to understand the science better, I recommend the Aquarium Science blog.

If you are wanting to get a balanced ecosystem in your tank, you will need to understand the science behind a balanced system, and test regularly. 

A balanced system works in a circle, and if one part gets out of whack, then the entire system can crash. 

Underfeed? Fish will not produce as much poo, which means less food for beneficial bacteria, so some bacteria die back, and less food for plants so some leaves are sacrificed. If we, the aquarium keeper see this, and compensate by overfeeding, then there is no longer enough beneficial bacteria to break down the extra food, and an ammonia spike happens. 

I adore the store in the Bay area, that hasn't done a water change in over 20 years. However, he's catching fish and taking at least a couple of cups of water out every day, and replacing that water with fresh water that has minerals in it to keep plants and fish healthy and happy. 

There is a lot of responsibility and planning that goes into creating as balanced an ecosystem as possible. And a lot of research to understand how the cycle works, and what our responsibility is (as the humans with opposable thumbs) to maintain a healthy ecosystem.