Question about my fish tank?

Question

I have a 20 gallon fish tank with a Oscar and Algea eaters. Just in the last couple of weeks the water has been turning green. I cleaned the tank. Cleaned the filters. And it's still really dirty. Any suggestions? Please help!

Answer 1

What you are talking about is called green water. This is caused from too much nutrients and sunlight. Feed the fish once a day only what can be can be consumed in 3-5 minutes. No food should be landing on the bottom. When you clean the tank, only drain 1/4 tank of water and gravel vac 1/2 the gravel without stirring the gravel. Some of the bacteria needs to remain in the tank or the tank has to go through ammonia/nitrite cycle when you change too much water. This is stressful for the fish and can cause them to get sick. Only leave the light on 10-12 hours a day. Try feeding Formula 1 or Formula 2 frozen cubes, which are available at pet stores.

Answer 2

Causes for green water:
Not enough partial waterchanges
Overfeeding
Overstocked
Inview of sunlight
Too much regular light
Excess phosphates in watersource

Your problem is you are overstocked. Oscars need 70 gallons PER fish. Both oscars and algae eaters excrete ALOT of ammonia. Common plecos get 2 ft long whereas oscars get 12-14 inches long. Algae eaters do just that, they eat green algae growing on things, not poop and honestly the amount of ammonia they excrete, they arnt worth it. If you do regular partial waterchanges you arnt going to have alot of algae growing on stuff.

You need to upgrade tank size or find the fish new homes.

NEVER EVER do a 100 percent cleaning. You just killed all of the nitrifying bacteria and are going to have to go through the cycling process all over again. The fish will have to endure their gills burning from the ammonia spike and nitrite spike. They will probably die.
TO get rid of green water without chemicals, cover the fish tank up and turn the light off for 4 days, leave the filter running but dont feed the fish and dont lift the blanket at all. No light whatsoever will kill the algae spores in the water.
Because you killed all the bacteria the water is going to turn a white milky color and will go away on its own in 3-6 weeks.

Answer 3

You're experiencing an algae bloom, probably, in your case, caused by excess nitrates. That oscar and possibly the algae eater (depending on what kind it is) will quickly outgrow that small tank. Ideally, you should look into at least a 75-gallon tank for the oscar alone. Now, suggestions for your algae issue will come from my normal answer for algae problems:

"Have you had your nitrates tested lately? If not, take a sample to your local pet store that sells fish and get it tested. Anything less than 40ppm is safe, but you want it less than 20ppm to inhibit algae growth. If it's more than 20ppm, you need to do a water change. You should be doing at least 20% a week. If your nitrates are too high within a week's period, chances are, your tank is overstocked. Also, consider cutting down on feedings. If you're feeding your fish daily, consider feeding them every other day or every third day. Excess food will contribute to high nitrates as well.

If your tank is in direct sunlight, consider moving the tank or closing the curtains/shade. Also, leave your aquarium light off for a couple of days. Algae needs light to grow. You take away the light, you can't grow any algae.

Consider planting some live plants like java fern. They will help convert the nitrates into food for themselves.

Lower your temperature to mid-70s. Be careful not to lower anymore than 4 degrees a day, or else you run the risk of messing with your fishies' immune systems. And we don't want any sick fishies.

Ghost shrimp are known to eat algae, and they add practically nothing to your bioload. And they're cheap.

Do not get any algae eating fish, like a pleco. Depending on your tank size (if it's anything less than a 55-gallon), they will quickly outgrow your tank.

And if all else fails, and you have to add chemicals, make sure you get an algicide that does not contain copper, as some fish are very sensitive to it, and it's quite difficult to remove. I recommend Algae Magic by Weiss, as it's organic and safe for all fish, plants, and invertebrates."

Also, you should never do a complete water change on any tank, as this will likely disrupt the biological filter and cause ammonia/nitrite spikes (which can cause permanent damage to your fish).

Good luck.

EDIT: JO, your fish are trusting you with their lives, and you are simply abusing them. Koi need ponds. They simply will not grow or thrive in tanks, especially anything less than a 250-gallon tank. Your ignorance is killing your fish.

Answer 4

Oscars are notorious waste producers and messy eaters and really have no business being in a 20-gal. 75gal+ recommended for these fish; 55-gal bare minimum (for sub-adult oscars).

Your tank has an excess accumulation of nutrients and waste due to keeping an oscar in a small tank. Your nitrates are probably off the charts as well.

Solution: Until you get your larger tank, conduct 50% water changes every other day. Keep nitrates below 20ppm.

Answer 5

Did you place it near a window or change the dressing on any nearby windows? Excess sunlight will make the algea grow quicker. You could also have an especially aggressive type of algea called spirolina (sp). There isn't any way to find out if you have it, the only thing you can do for it is get a better filter and change the cartridge more often until it goes away.

Answer 6

Ok as for all those people who say that Oscars need a 75 gallon tank, that is not true. I have goldfish and small koi about 14 in all in a 20 gallon tank, i put it right near the window, and yet there is no algae whatsoever. Word of advice, get an airpump. And get a 30 gallon filter. And done. Your lucky to have algae. My snails are starving.

Answer 7

Keep it out of the sunlight. I cleaned the glass on my tank with a pair of scrubbing magnets. I held the one on the outside of the glass while the one on the inside scrubbed the glass. I hope your filter is an external filter because of the bigger tank. You can buy something that cleans the gravel. It is a clear tube and sucks up a section of gravel and cleans all the debris from the gravel. There is a lot of dirt there. It's been a long time since I had an aquarium.

Answer 8

continue to do water changes... What are you feeding the oscars? They do poop alot, and the algae eaters are not "poop" eaters... they eat ALGAE.... so make sure you keep the water clean! Get a bigger filter if needed.
Are you cleaning the rocks too?

Answer 9

You can buy "algae fix" (from Petco or Petsmart)- just use a smaller dose then the tank-size on the directions calls for because you don't want to harm your algae eaters. Is you tank exposed to sunlight? Sunlight will cause algae to bloom which will turn your water a murky; swamp-water-esq green. if that is the case try to limit the amount of sun the tank gets. hope this helps

Answer 10

The green color is due to algae keep an algae eater or keep the light bulb off.