I have a 10-gallon aquarium with 5 tetras. It has artificial plants (plastic), standard aquarium gravel, a filter/pump (Aqueon) that hangs on the top of the aquarium. So it’s nothing fancy-schmancy.
The aquarium has developed black algae in the last 3 months or so. At least that’s what I have concluded. It comes off in small sheets off of the glass when I use my scraper thing. It’s growing on the plants almost like spiderwebs. Some of it is a long thread that has a small fringey thing on the end.
I’ve cleaned the tank twice - using a vacuum on the bottom and removing about 3/4 of the water. I soaked the plants, heater, and filter in bleach and hot water rinsing them thoroughly afterward. The algae returns after about a week or so. I’m guessing that’s because it’s still lurking in the 1/4 tank of water and gravel. I feel like I should do a total tank re-start. Remove all water, new gravel, etc. But I’m afraid it will kill the fish once I put them back in since there will be no good bacteria in the water anymore. I had a heck of a time starting the aquarium. Fish were dying left and right.
The tank never had black algae before. I would get the standard green algae and would have to clean the tank maybe every 6 months. This stuff is out of control.
Cutting down the time the tank is exposed to light will help. Real plants will compete with the algae.
A blackout will stop the algae, cover the tank with black trash bags overnight. It once took me three days of blackout to rid a tank of algae.
I didn’t do any cleaning before I covered it up. You do want to be sure there is surface exchange of oxygen, you are just blacking it out, not sealing it up. Of course, I peeked at them every few hours to be sure they were ok. At the end of the blackout there will probably be some dead algae to be cleaned up.
A blackout will definitely do it (and the fish won’t care at all). And real plants will help to prevent it from coming back.
But for it to just appear suddenly if nothing else changed is a bit strange–you need to figure that out, or you will definitely have ongoing problems. I flinched when I read about cleaning everything with bleach. Especially if you bleached the filter, you probably killed a large amount of your beneficial bacteria. That (cleaning with bleach) is not something you really ever want to do for algae, or really for almost any other problem unless you’re completely breaking down the tank for good.
You really don’t want to get rid of the algae, you want to get rid of what is causing it to overgrow. That’s almost always a matter of too much light and/or too much nutrients (usually from overfeeding). Somehow one of those two things changed to cause this problem.
But you can solve those problems. Light is easy–the blackout lets you restart and then you can very gradually start having lights again. What lights are you using and for how many hours? (Especially be careful about sunlight coming in through any nearby window).
You can also cut back on feedings–you should not be feeding more than the fish eat in a minute or two. And you can step up the water changes. If you’re doing 10-20% once a week, make it twice a week. If you’re doing twice a week, do it three times a week. Those two together will usually do the trick. Then you can gradually go back to a less intense water change schedule.
You’ve got a pretty small tank–so definitely don’t add any fish. But it might also be helpful to add some snails or shrimp. They will eat algae and any uneaten food. Amano shrimp in particular are great for eating up algae. They won’t clean it all up if it’s overgrown, but they’ll keep it under control once you get it that way. Also they’re cool and fun to watch and hardy and readily available. Your tetras (neons, I’m assuming?) might nip at the shrimp a little, but it’s usually not a problem.
And one more vote for real plants. Guppy grass (naja guadalupensis) is fantastic for this. It’s pretty, grows like mad (you will have to trim it regularly) and will suck up all the nutrients that would otherwise feed algae. And the fish will like to swim and hide in it (it floats, although you can plant it. But floating is better).
Thanks for the OP for giving me a reminder of why I don’t miss my aquarium decades!
Only partly serious, but I remember dealing w/ algae black/blue and green. Not fun.
Once I went planted, I couldn’t understand why anyone would stick w/ plastic. No need to go down the CO2/substrate/lighting/additives rabbit hole (tho I certainly did!) For a long time, my most bulletproof tank was a 3g at work, w/ java moss, anubias, and some crypts, Endlers and cherry shrimp. 7W bulb, no heater, HOB filter, no CO2/additives - NO PROBLEMS!
With all the deep cleaning, you’re never finishing the nitrogen cycle and the problems associated with that will never go away until the cycle is complete. Get rid of the plastic plants and put in some real ones. Beginner plants like Java fern and Anubias have rhizomes and so don’t need to be planted under the substrate, instead they get their nutrients from the water column.
Don’t add any new occupants until your nitrogen cycle is complete otherwise they will keep dying. Keep checking your water parameters twice a week until the cycle is finished. This can take a couple of months.
Consider adding a little diversity to your tank. 10 gallons for 5 tetras has room for more fish.
Add a couple of small catfish, they won’t grow beyond a couple of inches. If you have smooth pebbles rather than sharp, crushed rock, add a couple of Coolie Loaches. They won’t eat the algae but will keep the gravel stirred because they like to burrow. This will not hurt any plants that you add. They are social fish so add two rather than one.
There are various algae eaters but many will outgrow a 10 gallon. A community tank, with more fish, will have a more balance ecosystem. My opinion is that 5 tetras and nothing else is part of the problem. But I understand that you would like the get the algae problem under control before wasting money on more fish.
This. You don’t get rid of algae; you get rid of the causes of the algae. Algae in aquariums grow due to a combination of light. nitrogen nutrients, phosphate nutrients, and potassium nutrients.
Cut down on the number of hours the aquarium is lit. If you don’t have them handy, pick up a bottle of 5-in-1 water test strip kits (it’s good practice to test your levels every so often, anyway); get one that measures Nitrite, Nitrate, and KH (the other two measurements are usually pH and GH). Note that KH is really a measurement of buffering capacity, but phosphate is typically a significant component of KH in many aquariums. >50 parts-per-million Nitrate and KH with decent lighting, you’re going to get algae.
For good measure, whip up a batch of treated water as you’d usually do during water changes and test-strip that too; always possible that nutrients are creeping in that way.
More good advice! I think I’m going to try some live plants. I was under the assumption that live plants would create more crud in the water. I also want to get more fish, but will wait until I get the tank under control.
Are there any good algae eaters that won’t grow too big for the tank? I’ve never had any luck with snails - they never lived very long. I’ve also heard horror stories of snails reproducing like crazy.
I turn the light on in the morning and usually turn it off around 2:00. But the tank is in a room with a window. I’ve blocked the side of the tank that is directly facing the window with one of those picture sheets. Other than putting the tank in a closet or in the basement there will always be some light. And how do you enjoy an aquarium if the lights are off and it’s somewhere where you’re not!?
I sometimes wish I could get rid of it. It’s a vicious circle. When one or 2 fish die, I feel like I have to replace them for the sake of the living fish!
“I turn the light on in the morning and usually turn it off around 2:00”; 2PM or 2AM? 8-12 hours of light a day is plenty.
Don’t get into the rat-mongoose trap with algae; just deal with the algae. If you enjoy algae eaters for their own sake, then great; there are some smaller ones suitable for 10 gallons. But algae eaters are not a substitute for regular water changes, proper water chemistry monitoring, and other regular maintenance.
