29 gallon bad smell coming from tank

I have a 29 gallon tank planted with 5 gouramis, 1 red tail shark catfish, 1 pleco, and 2 clown loaches. The clown loaches are in there temporarily. I noticed a bad smell coming from my tank a couple days ago and I did a big water change and gravel vacuumed as much as I could. I have a HOB filter running all the time and also a big sponge filter running in the corner. So I have good filtration going. The smell went away mostly until I smelled again today and the smell is back but not as bad as before. Whats the cause? I've been feeding a lot of algae wafers lately. Could that have something to do with the smell? How can I keep the smell down permanently and what has worked for you guys in getting rid of a bad smell in a fish tank.

 

If you don’t already have it, I’d suggest putting carbon in your filter.

 

If you don’t already have it, I’d suggest putting carbon in your filter.

Now that I think about it I had carbon in my filter a couple weeks ago. Does the carbon help with a bad smell?

If you don’t already have it, I’d suggest putting carbon in your filter.

Also, so many people don't use carbon. How do they not have an unpleasant smell develop?

 

Also, so many people don't use carbon. How do they not have an unpleasant smell develop?

You‘re right, many people don’t use it, but it should take your smell away.

Activated Carbon for the Aquarium

 

Carbon traps everything indescriminately toxins, odors, nutrients, tinted water etc

If you have adequate bio and mechanical filtration you should not need carbon unless you are trying to mop up a medication or something temporarily.

 

Two things, if your Plecos is a common Plecos, it is trapping food and poop under the substrate, making a smell. Also, use a carbon filter as said above if you don’t want to change your substrate.

 

Only reason I've come across not to use carbon is if you use plant ferts. I'm guessing once your tank is well mature the smell will go anyway. Keep an eye out for cyanobacteria between the glass and substrate too.

 

and if your using a lid make sure to clean that and the rI'm of the tank so you don't have any old fish food sitting on it. And be sure to do a daily head count. A rotting dead fish will leave a rancid smell if the other fish don't make quick work of it.

 

How long have you set ul the aquarium for? What does it smell like?

 

How long have you set ul the aquarium for? What does it smell like?

About two months. Its fully cycled though. Been 0ppm for ammonia and everything else for a long time. It just smells bad. I can't really describe it. Just not a pleasant smell and I know what a fish tank should smell like.

 

Tank seems way overstocked in terms of fish size and bioload. Carbon is a band-aid solution, the root cause of your problem is likely the huge bioload for a 29 gallon tank. What kind of pleco do you have? What are your nitrate readings? Does the tank smell like rotten fish?

 

It's possible the smell is from a build up of algae or decaying organic matter.

But a pack of Mr. Clean Magic Erasers ( or generic HDX brand from Home Depot).

Use them to clean the waterline of the interior glass, the inside of the lid, the upper plastic brace, etc.

The work great to clean heaters, filters and decor. I use them myself, amd recommend them to anyone

Also, give your substrate a good vac with your siphon.

 

Tank seems way overstocked in terms of fish size and bioload. Carbon is a band-aid solution, the root cause of your problem is likely the huge bioload for a 29 gallon tank. What kind of pleco do you have? What are your nitrate readings? Does the tank smell like rotten fish?

It's not overstocked all these fish are like baby fish compared to their future sizes. The pleco is a common pleco. I don't like to test nitrates too often just because if I tested every day or every other day I would run out and have to buy new test kits too often. So I test every now and then but do water changes often. The water changes should keep nitrates in check so it shouldn't be an issue. No it doesn't smell like rotten fish. Maybe decaying organic matter would describe it better.

 

If it smells like that a buildup of anaerobic bacteria may be your culprit, although I'm not sure. What kind of substrate do you have?

 

If it smells like that a buildup of anaerobic bacteria may be your culprit, although I'm not sure. What kind of substrate do you have?

I got the standard gravel and also put a bag of black substrate pieces mixed in that are supposed to be good for planted tanks. The black substrate isn't gravel but i'm sure you know what i'm talking about. And yeah the smell isn't overwhelming or necessarily disgusting smelling but it's not like a great clean smell.

 

I'm not so sure then, anaerobic bacteria is common in sand or dirt but I don't think it can grow in gravel?

 

I would test your water more often. Especially since your tank is new. I would not feed so much algae wafers. Maybe once a week. Since your tank is new, I would change your filter carbon once a month. They only last about a month and then they do not trap smell anymore.

 

Even as juvies, its still a relatively high bioload. People even have issues with keeping smaller plecos in a 29 gallon due to the amount of waste since they constantly grazing.

Anaerobic conditions can still develop in gravel, if its not appropiately maintained (vacuuming and having rooted plants)

 

I would suggest at a minimum to do a thorough cleaning of the gravel. It's possible a build up of decaying organic matter is in the gravel, causing the offending smells

If you have the time, during the next large water change, remove all decor and wash separately and remove the gravel to also rinse out with a bucket and garden hose.

In our first tank, we had gravel in a 20g. That tank has been decommissioned for now, all our other tanks use Quikrete Pool Filter Sand as substrate.

In my experience, the gravel was a black hole sucking down all the detritus and uneaten food. The corydoras couldn't get to the uneaten food because it would sink into the gravel.

It was a PITA to always gravel vac thoroughly.

After using sand in the other tanks, it is a lot easier. Waste accumulates on the top of the sand, making it very easy for bottom feeders to get to, and to suck up with a siphon vac.

 

When cleaning the gravel I'd be careful, if there is a buildup of poisonous gasses from anaerobic bacteria it could hurt your fish if disturbed all at once, Do multiple more gentle cleanings of the gravel over time as opposed to one big one where you get everything out all at once.