Smell coming from 8 gallon aquarium

Hi All,

Specs:
8 Gallon Tank
Sponge filter
Guppies and Neon Tetras
No Substrate
No lights
No lid
Guppy grass(only plant)

Recently I have noted that when I turn off my filter(for feeding), a light smell comes from my aquarium. I use well water in my aquarium which is mineral rich and good for fish. Recently lost 3 guppies in successive days. Cleans sponge filter every 20 days until the water taken from aquarium is clear after rinsing it. Is the smell normal and I am sensing it because I have no lid? Please advise.

 

Most aquariums have a slight smell to them. Earthy might be one description (pretty sure there was a thread dedicated to aquarium smells somewhere!)

Not sure why you turn your filter off when you feed though - I’d be worried about remembering to turn it back on!

Edit - there was a thread:

How would you describe your fish tank smell? | Freshwater Aquarium Discussion Forum | 493242

 

Thank you for you response.

I turn off the filter so the fish could easily grab the food. Also, I love watching them eat. And turn it on after five minutes. I will refer the thread you've suggested.

I set up this tank a year before. Is it time I should completely wash the aquarium after moving the fish to another tank? Also, the water color here is slight yellow and hence the photo looks so.

 

I wish someone please reply on the below as I get continuous smell when I turn the filter off these days.
"I set up this tank a year before. Is it time I should completely wash the aquarium after moving the fish to another tank?"

 

I wish someone please reply on the below as I get continuous smell when I turn the filter off these days.
"I set up this tank a year before. Is it time I should completely wash the aquarium after moving the fish to another tank?"

I don’t think you need to completely clean your tank. Doing that will probably do more harm than good to be honest so I’d recommend against doing that really.

What is the smell like? If it just smells like a fairly typical aquarium like others have described then I don’t think that there is much cause for concern.

 

It smells weird. When I accidentally passed my nose over the aquarium, I almost felt to vomit. I searched for any dead fish. But there is nothing. I removed all guppy grass to get a clear look. Now it's only the fish, water and a sponge filter and nothing else. Even after replacing 75% of water the smell prevails. Oh I almost forgot to mention!! I have some shells(5) at the bottom. Is that the cause?

 

Does it smell like rot or ammonia? Aquariums will always have a bit of a smell to them but it's only a problem when it actually smells like death.

 

test your water, maybe get an idea of what's going on. if something is spiking ammonia or nitrites or nitrates. maybe some dying plant or old food in the substrate.

You don't menton water tests, or water changes, just cleaning the filter sponge, so more info is needed.

My tank will pick up a slight dead fishy smell if I need to vacuum up uneaten food and some poop. if I let that go, it would get stronger for sure.

 

Do you have active carbon in the filter, weather old carbon that needs to be replaced or put some carbon in to help clean things up.

 

I had one tank that developed a musty smell. It was only noticeable when you put your nose right above the water, but regular water changes and normal cleaning of the filter would not make it go away. For other reasons I eventually tore it all down and installed new gravel. (same filter and media) No more musty smell. Most of your BB is in your filter, I would not be afraid to try a full tear down/clean out.

My guess is your smell is coming from your well water. Do you have any other tanks running to compare with?

 

test your water, maybe get an idea of what's going on. if something is spiking ammonia or nitrites or nitrates. maybe some dying plant or old food in the substrate.

You don't mention water tests, or water changes, just cleaning the filter sponge, so more info is needed.

My tank will pick up a slight dead fishy smell if I need to vacuum up uneaten food and some poop. if I let that go, it would get stronger for sure.

The test results are normal. Also, it's a bare bottom tank with no plants. And as mentioned earlier, I changed 75% of water.

Do you have active carbon in the filter, weather old carbon that needs to be replaced or put some carbon in to help clean things up.

Do you man ceramic rings etc? I only have the sponge filter. No food waste or fish poop. I clean it everyday using a sucking pipe. As these fish are small very less waste is produced.

 

What does it smell like? Can you compare it to something or describe it? That may be able to help us identify the source

 

The test results are normal. Also, it's a bare bottom tank with no plants. And as mentioned earlier, I changed 75% of water.

Do you man ceramic rings etc? I only have the sponge filter. No food waste or fish poop. I clean it everyday using a sucking pipe. As these fish are small very less waste is produced.

Maybe check under the lip up top? Its gets a super stinky build up under there that you just dont ever see.

 

my tank is bare bottom and no plants for raising fry. I get that bad smell when food and waste is sitting too long. I I've got over 100 near half inch angelfish fry in a 20g. and doing 20% change/vacuum daily, and running a sponge filter.

I get a smell coming up on the 24 hour mark from the days waste starting to break down, My tests aren't just "normal" my tests are zero to .25 ammonia/.25 nitrite/ 5ppm nitrate but not even dark enough for those higher readings.

it shouldn't be 'vomit inducing" at that point, but should be a fishy, off smell lightly, and I'll get hit with it when I open the lid at first. but I'm crowded, I feed a lot of times, they poop a lot, there's a nice thin layer of uneaten food and poop each day that needs to go,

No idea why you'd do a 75% water change, it's too much at once unless you have a severe water quality issue to address.

I'm at a loss for what your problem really is here. you have a complaint of a problem, but seemingly no reason or cause of what makes the problem happen, and it shouldn't be happening without a cause.

I don't know..... did you check good around the outside of the tank for jumpers? maybe you get a jumper without a lid occasionally, and he's drying out and decaying in the shadows behind the tank or something.

 

The advantage of using well water for aquariums is that it does not disinfected with chlorine, so you do not have to worry about dichlorinating the water. Unfortunately, unless you have your water tested periodically, you may not know what is in the water. If you live in an agricultural area, the water might contain runoff of fertilizer and pesticides. It can also contain sulfates or sulfides that can cause weird aromas in an aquarium.

Unlike many fish, guppies like hard water, so if your well water is hard, that should not be a problem.

Since your aquarium has no substrate and few decorations or plants, your filter is the primary biological filter. A sponge filter is very efficient, but when cleaning the fliter do not try to get it super clean.

By any chance, were the shells at the bottom of the tank once live snails? If snails die, that is one of the worst aromas you will ever smell. Pick up each of the shells and sniff them. If they do not smell, put them back. If they smell, throw them in the garbage.

Most aquariums do not require activated carbon, but carbon is great at absorbing bad smells. Carbon works best if placed in a filter so water flows through it, but since you only have a sponge filter, you can just get a mesh bag of activated carbon, rinse it out with tap water (since you do not have to be concerned with chlorine) and place it on the bottom of your tank. Just leave it there as it will also provide an additional surface area for the growth of beneficial bacteria. You can rinse it out from time to time (but not at the same time as you clean your sponge filter). If the water starts to smell again, you can add new carbon.

Are you overfeeding your fish? That is easy to do in a small tank. The fish should consume all the food in just a few minutes. If they do not, you are feeding too much.

 

I had one tank that developed a musty smell. It was only noticeable when you put your nose right above the water, but regular water changes and normal cleaning of the filter would not make it go away. For other reasons I eventually tore it all down and installed new gravel. (same filter and media) No more musty smell. Most of your BB is in your filter, I would not be afraid to try a full tear down/clean out.

My guess is your smell is coming from your well water. Do you have any other tanks running to compare with?

Yes, my issue is almost the same. Sorry I didn't understand what you mean by "BB". I don't have other tanks with well water.

What does it smell like? Can you compare it to something or describe it? That may be able to help us identify the source

It smells like dead fish. I searched for dead fish around the tank also. Nothing found. My sponge filter is 8 months old. Could that be the issue?

Maybe check under the lip up top? Its gets a super stinky build up under there that you just dont ever see.

No top lid for the aquarium.

my tank is bare bottom and no plants for raising fry. I get that bad smell when food and waste is sitting too long. I I've got over 100 near half inch angelfish fry in a 20g. and doing 20% change/vacuum daily, and running a sponge filter.

I get a smell coming up on the 24 hour mark from the days waste starting to break down, My tests aren't just "normal" my tests are zero to .25 ammonia/.25 nitrite/ 5ppm nitrate but not even dark enough for those higher readings.

it shouldn't be 'vomit inducing" at that point, but should be a fishy, off smell lightly, and I'll get hit with it when I open the lid at first. but I'm crowded, I feed a lot of times, they poop a lot, there's a nice thin layer of uneaten food and poop each day that needs to go,

No idea why you'd do a 75% water change, it's too much at once unless you have a severe water quality issue to address.

I'm at a loss for what your problem really is here. you have a complaint of a problem, but seemingly no reason or cause of what makes the problem happen, and it shouldn't be happening without a cause.

I don't know..... did you check good around the outside of the tank for jumpers? maybe you get a jumper without a lid occasionally, and he's drying out and decaying in the shadows behind the tank or something.

I did the water change of 75% only after losing 3 guppies in successive days. Usually I do only 15% water change everyday where 15% of old water including food waste (if any) and fish poop gets replaced by 15% of fresh water. No jumpers seen around.

The advantage of using well water for aquariums is that it does not disinfected with chlorine, so you do not have to worry about dichlorinating the water. Unfortunately, unless you have your water tested periodically, you may not know what is in the water. If you live in an agricultural area, the water might contain runoff of fertilizer and pesticides. It can also contain sulfates or sulfides that can cause weird aromas in an aquarium.

Unlike many fish, guppies like hard water, so if your well water is hard, that should not be a problem.

Since your aquarium has no substrate and few decorations or plants, your filter is the primary biological filter. A sponge filter is very efficient, but when cleaning the fliter do not try to get it super clean.

By any chance, were the shells at the bottom of the tank once live snails? If snails die, that is one of the worst aromas you will ever smell. Pick up each of the shells and sniff them. If they do not smell, put them back. If they smell, throw them in the garbage.

Most aquariums do not require activated carbon, but carbon is great at absorbing bad smells. Carbon works best if placed in a filter so water flows through it, but since you only have a sponge filter, you can just get a mesh bag of activated carbon, rinse it out with tap water (since you do not have to be concerned with chlorine) and place it on the bottom of your tank. Just leave it there as it will also provide an additional surface area for the growth of beneficial bacteria. You can rinse it out from time to time (but not at the same time as you clean your sponge filter). If the water starts to smell again, you can add new carbon.

Are you overfeeding your fish? That is easy to do in a small tank. The fish should consume all the food in just a few minutes. If they do not, you are feeding too much.

Yes, guppies like hard water as you said. No, I don't live in an agricultural area. Also, I clean sponge filter every month with the same aquarium water and don't make it super clean.

Yes, the shells at the bottom of the tank once were live snails(I assume). I got it from the beach (only the shells).

By carbon, do you mean ceramic rings? Can you attach an image so I can go to a shop and buy it?

I think I was overfeeding the fish (twice a day). But after the issue I feed them minimum and remove any food afloat after 3 minutes (rarely happens). I believe that such fish consumes their required food in a maximum span of 3 minutes.

I will smell the shells and update you shortly.
Attaching an image of a similar shell that I placed in the aquarium:

 

Maybe check under the lip up top? Its gets a super stinky build up under there that you just dont ever see.

This as StarGirl says above. if your tank has a rim around the top, some really funky mold and slime and gunk can build up there on the top of the edge or under the lip on the inside where the water can splash or just drip off there with evaporation and the bubble water movement.

The fishfood is basically dead fish and algae and stuff like that, when it decays it does create a stink, maybe the rim edge has something hiding under it.....

this is another good place to look for it.

 

I agree about top rim part. I clean mine about every 2 weeks with paper towel on tanks. there's a grime build up.

also since your tank is bare bottom, you have less beneficial bacteria because there's no gravel for it to grow. It's nice for aesthetics but you do miss out of the colonization of bacteria by no sand/gravel.

I added ceramic media under my gravel in my 15 truval and huge difference ( in addition to the ceramic media the tank came with to put by pump). It was a huge difference IMO . My water changes are minimal fuss and with use of floating plants, the cycle start was a breeze

Question: did you boil the shells before adding them?

just like the magnolia leaves I self prep, there's stuff living on it. boil 20 minutes, seal in a mason jar with water for 2 days ( no to minimal oxygen source), then dry & use. kills off everything.

 

Sorry I didn't understand what you mean by "BB". I don't have other tanks with well water.

Beneficial bacteria. This is mostly in your sponge filter even if you had gravel.

Your well water is the big unknown here ...as it can contain all kinds of things. Have you ever had it tested? What does it smell and taste like?

 

Hi. all,
I see around 17 guppies or neons in a 8 gallon with what looks to me to be a minimum size of sponge filter. Plus the 3 dead this week

There does at least in the picture appear to be fish swimming at the surface.???

Please don’t think I am picking on anyone for having fish in small tanks. I am not. Here’s a quick snapshot of rice fish in a 5 gallon . Note the size of the sponge filter I use in all tanks.

 

It's the SHELLS. I removed all of them. Also changed 50% of water. Now there is only a minimal smell which I think will be gone in some days. Thank You All.

This as StarGirl says above. if your tank has a rim around the top, some really funky mold and slime and gunk can build up there on the top of the edge or under the lip on the inside where the water can splash or just drip off there with evaporation and the bubble water movement.

The fishfood is basically dead fish and algae and stuff like that, when it decays it does create a stink, maybe the rim edge has something hiding under it.....

this is another good place to look for it.

Not much junk there but cleaned it.

I agree about top rim part. I clean mine about every 2 weeks with paper towel on tanks. there's a grime build up.

also since your tank is bare bottom, you have less beneficial bacteria because there's no gravel for it to grow. It's nice for aesthetics but you do miss out of the colonization of bacteria by no sand/gravel.

I added ceramic media under my gravel in my 15 truval and huge difference ( in addition to the ceramic media the tank came with to put by pump). It was a huge difference IMO . My water changes are minimal fuss and with use of floating plants, the cycle start was a breeze

Question: did you boil the shells before adding them?

just like the magnolia leaves I self prep, there's stuff living on it. boil 20 minutes, seal in a mason jar with water for 2 days ( no to minimal oxygen source), then dry & use. kills off everything.

No, I didn't boil the shells. My mistake.

Beneficial bacteria. This is mostly in your sponge filter even if you had gravel.

Your well water is the big unknown here ...as it can contain all kinds of things. Have you ever had it tested? What does it smell and taste like?

Well water is fine here. Have tested it.

Hi. all,
I see around 17 guppies or neons in a 8 gallon with what looks to me to be a minimum size of sponge filter. Plus the 3 dead this week

There does at least in the picture appear to be fish swimming at the surface.???

Please don’t think I am picking on anyone for having fish in small tanks. I am not. Here’s a quick snapshot of rice fish in a 5 gallon . Note the size of the sponge filter I use in all tanks.View attachment 841594

I ordered another tank to which I will move the guppies shortly. I assume that you were telling me to change the sponge filter to a bigger one. Kindly confirm. Thank you.

 

Yes you could use a bigger sponge filter if that’s going to be your only filter. But having two is another way of making sure one was cleaned recently and one could be cleaned in a few weeks time.

I know my filter is ridiculously large for that 5 gallon but I have chosen to run the same size filters in all tanks.



Actually a quick snapshot of how it’s comm practice to stack two sponge filters on top of each other that take up not much more room and still only need the one air line.

 

Shells are made largely of calcium carbonate. The structure is porous, so they tend to absorb odors and can then release them later. That sounds like what has happend in your case.

Just place them in boiling water, perhaps with a splash of vinegar, for about 15-30 minutes. That should improve the situation.

 

Yes, I don't think I will add shells anymore. I added back the guppy grass and now it's all good and green. All the fish are active. Thank you all. Hope this thread helps someone someday. Peace

 

Yes, I don't think I will add shells anymore. I added back the guppy grass and now it's all good and green. All the fish are active. Thank you all. Hope this thread helps someone someday. Peace

There is nothing wrong with shells as long as they are cleaned first. Just don't pick them up off the beach and toss them into your aquarium.