how often do you clean your tank? (meaning gravel cleaning and wiping down the sides) Sounds like mold/fungus that grows because of leftover food. A good cleaning and water change (or two) should take care of it.

Not very often, but there's only one fish in it, it doesn't get that dirty. I thought it might be some kind of mold, but does mold grow in water? And it's on the glass, too, where there isn't anything organic for it to grow on... It doesn't seem to be bothering the fish.

WW

I can only guess it's a type of filamentous algae , which tends to grow into fine threadlike colonies, but those usually are a very light green all the way to dark green, and usually would come with high nutrient levels in the water. Under lower light conditions , they'd most likely have less chlorophyll , so they could appear almost white. In generally they're totally harmless in an aquarium, though sort of unsightly.

Even small aquariums with few fish need gravel vacuumed. You can get away with it in a planted aquarium with rooting plants for longer then a nonplanted. Nonplanted should be vacuumed every week (because it is a small tank) with 15% PWC. I think bird hit the nail on the head. If you dont change water at least bi-weekly the nutrients and organics will build causing enabling the algae.

Are you sure you didn't get any bong water in the aquarium?

How often is not often? Even with just one fish, say he doesn't eat all his food - even if it's a pellet or two every day. All of that will build up and there's the environment for mold (or maybe it's just a mold-like organism?)

Here is a link that might be useful: overfeeding

Hm, their mold/fungus description might be it. Alhough it's more web-like than cottony. Guess I need to vacuum more often. I have been feeding more than he eats, he's got a swim bladder problem and tends to go after what floats down past him rather than swimming up to the surface like he used to. I'm afraid he's not getting enough so I've been overdoing it a little.

Don't snails eat leftover fish food?

WW

Not necessarily. Snails may simply go after algae first. Don't count on snails or even bottom feeders to always eat up old food. If the food is old and decomposing, they won't want to eat it either.

snails leave a mucus trail behind them could this be it?
or perhaps the snails are breeding?
the 4 gallon issue always bugs me. no animal should be kept in anything under 10 gallons, and even 10 gallons is far from ideal. a 4 gallon mini aquarium is just as bad as a fish bowl, it may have filtration but there is not enough water to support a healthy colony of beneficial bacteria.
a tank that small should be syphoned at least twice a week.
even my 220 gallon tank gets syphoned once a week (30 percent) and thats a huge tank!
a tank that small is a living toilet. drain the tank clean it thoroughly get rid of the snails and replace your filter media and gravel. start all over. the fish will finally be able to breathe again. he will survive the cylcing period 99 percent of fish do. but you must and i mean must syphon that mini tank twice a week, there are no ways around it.
for 50 dollars you can get a complete 10 gallon setup, id go with that
4 gallons=cruelty

Sassy: I agree with your assessment of Betta cultivation but would like to add that life in a rice paddy, with all the elements of rain, sun, natural intercgange of gases, food, filtration, etc... needs a little help in the small, artificial environment that we hobbyists provide. I would recommend a small sponge filter to remove Ammonia and Nitrites, even though their labrynth system can inspire atmospheric air. They are territorial but also shy. Rpoviding plants for their comfort would also be helpful. It would help toward providing less stress and susceptibility to ich or bacterial infections.

I also have this white web-like stuff in my small tank. This is my second round with this stuff! The first time I had just put 3 red tail platy fish fry into the tank from a nursery in a 10-gallon. After about three days, this stuff formed and ended up killing 2 out of the 3 fry. I put the one fry back into the nursery, completely cleaned out the tank (replaced the gravel too), and re-established it for two weeks. Than I tested it, found it to be fine, and put some more platy fry into the tank. Again, after a few days, this white stuff formed. This time, I immediately removed the fish back into the original nursery after loosing one. I went to a nearby Petco and asked their advice. They were stumped! All they could recommend was cleaning out the tank and using bleach to kill any living fungus, bacteria that might be in the tank. There was some left-over food in the tank both times as well. So, I am stumped too! Does anyone know what this stuff actually is?

III................ THINK I HAVE MOLD GROWING OFF MY ROSY RED FEEDER FISH!!!!!!!!!!!!!!!! CAUSE I GAVE THAT SAME FISH PELLETS BUT HE DIDN'T EAT HIS PELLETS AND ONE DAY WHEN I CAME HOME FROM SCHOOL THERE WAS SOMETHING GROWING OFF THE PELLETS AND I THOUGHT FOR A MOMENT .... AND I'M LIKE MOLD!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! AND THEN YESTERDAY WHEN I WENT TO A CHRISTMAS PARTAY AND CAME BACK/might be sad/THERE WAS LIKE COTTONY/WEBBY/STUFF ON HIS TAIL OVER HIS DIGESTIVE SYSTEM AND IT IS ALL MOST TO THE TWIN FINS ON THE BOTTOM OF HIM AND MY ETHER FISH IS/VERY SAD KINDA BUT PAINFUL FOR SPIKE ON THE TOP OF HIS BACK TAIL HE'S LOSING PARTS OF HIS...TAILL AND MAYBE EVEN HIS TOP FIN

Here is a link that might be useful: CAN MOLD GROW ON FISH

I have that white stuff at the bottom of my fish tank to it looks like cotton webs and it started growing first when my mom and dad brung home a puffer fish from petco and like a week later I found it at the bottom of are fish tank with that white web all around him and his eyes where white. We Flushed him down the toilet and now it's all over the bottom of my fish tank and I can't find my sucker fish. Is their anyone who had this and learned how to get rid of it without getting a new. Fish tank.

You probably have a slime mold in your tank. Slime molds feed on decaying organic matter and are not dangerous for the tank inhabitants. I had a yellow slime mold show up on the glass of an aquarium once but it only lived about two weeks and was apparently feeding on the biofilm that covered the glass.

Mike

Here is a link that might be useful: Slime Molds

I'm dealing with the same problem regarding the thin, whispy white film. I have a 1.5 gal tank for my betta and lit'l mystery snail. First noticed the algae on my new banana plant's baby-leaves. I've been working at a mainstream PetStore for about 6 months now and I trust my fish co-workers. It's a simple algae that can be cleared with a thorough cleaning & water change. If desiring more, beneficial bacteria drops can help further. If left alone..can cause serious havoc!

For the bettas; no tank is too big! Their natural "territory" in the wild is a space roughly 3x3 to 3x5 feet! Sadly, even in my own store, incredibly small tanks are on the market :( like how can a fish be happy in a .5 gal tank?! That's barely 2 of the cups they sit in waiting to be sold.

I have a 6.5 gallon tank. I had the same white stuff around some of the plants. I change about 33% of the water cleaned that white web and after 2 days I continue having it. Someone in my pet supply store told me it’s because the tank is exposed to too much light since I have it close to my balcony sliding door. I will clean it again and asked someone at Petco or PetSmart.

What you have is no from an unhealthy tank. Betta fish can tolerate that but it looks gross. You have to remember how waste from live fish are processed on a cyclical level. When water is dirty, meaning too much waste from fish or too much food, something has to eat that. If you don't fill your tank with fresh water regularly, meaning weekly water changes for 1 beta, the white stuff pops up because if an abundance of decomposing material. Also, a beta fish only need 1 (yes 1) flake of food a day to be happy any healthy. If you buy a small can of fish food. That should last literally two years regardless of what the instructions say. You are feeding the fish, not indulging it. Fish tummy's are the size of their eye ball. A flake is about the equivalent of 2 full meals. Fish don't understand the concept of love through gluttony. When food is wasted, it rots and mold or bacteria pop up to compensate for the rotten material. Like people, fish do not need to be full to be happy.

Also, snails are not necessarily pests. If you crush them up, you fish will love to eat the fresh meat they provide. A fish tank, regardless of what is in it, should never be in sunlight as the refraction of the glass or plastic hightens the rats of the sun to an unhealthy nature. A tank is not a pond or natural body of water. Light through plastic or glass creates an unatural energy source with odd results. A Betta is very comfortable on a shelf or quiet place with minimal light. Also,. When you clean the tank, every once in awhile (like bi monthly) put the Betta in a cup or bowl of the tank water (roughly 40 to 60% of the original amount) stir up the gravel a bit to release the bacteria that's building up down there with your hand. Usually a cloud of brown will be seen. Empty out that water about half of that water but not all (remember, bacteria is not as completely a bad thing). Then fiill the tank back up with fresh water and pour the fish back in with the original water it was in... Fish love fresh water, but they need some bacteria in their tank to be healthy. Also, and this is important, temperature is important as you don't want the fish to go into shock from a sudden temperature change. Think about your own body when you do this. If you are in a room that is comfortable temperaturewise, then you enter a freezing or hot room, your body reacts. Use your sense of touch when gauging whether the tap water is close in temperature to the original. If needed you can use a thermometer but I have never found that necessary. It sounds more complicated than it actually is. Just think of your fish as a living being that needs the same things you do.

For those who feel like 4 gallons is too small for a Bettas, have you ever seen some of the nasty ponds and even small puddles Bettas can be found in, or how nasty and dangerous those ponds can be? 4 gallons of a tank with clean filtered water where the fish is well taken care of, where the fish is happy and never has to worry about ponds that dry up (happens all the time in nature, not in a 4 gallon aquarium), killing hundreds of their kin, never has to worry about if there will be food shortages, or when food becomes scarce having to fight to the death (that is right, they kill each other fairly frequently in the wild), just to survive, or having other predators such as birds, mosquito larvea, frogs, snakes, etc hunting them and eating them. It is funny to me how some people feel they have the grand authority to tell someone who cares enough for their fish friend that they are being cruel, especially when they obviously care for the fish or they wouldn't be posting on a site like this knowing there is ALWAYS someone more willing to be negative, than to be helpfull.

I'm sorry but for the person yapping about keeping a Betta in a 4 gallon it's a far better home to than in the little cit they live in for months. Be nice to us can afford that 100 gallon tank but not very realistic for 1 fish ....

What is this? It's on my 37 gallon tank and my 5 gallon tank. It's growing on the glass inside the tank. I'm confused. We tried wiping it away but it came right back. I don't know how to get rid of it or if it's harmful to my fish. Please help.