NASTY, thick, black algae

sweetcoral81 · 05-21-2007, 06:55 PM

My kids have a 25 gallon fish tank with 5 goldfish. I've had fish forever so I know about basic care (at least I think I do

) but never before have I seen algae like this. The talk has a filter, a light, basic gravel and a few tank decorations. I add aquarium salt when I do water changes (I do 80% water changes about once a month, sometimes every two months). The fish get fed once a day. Any ideas why the algae is so bad? The water seems to stay fairly clean even when the sides of the tank and decorations are covered in the nasty algae. I just cleaned the tank again and this time I'm letting the tank and decorations sit w/o water for a day or so to let the stuff I missed dry out and hopefully die. Usually when I clean the tank, it stays clean for 2-3 weeks and then the stuff starts to take over again. Its been like this for a year now and its really frustrating. I just don't want to do anything that will kill the fish. Any ideas?

BJP · 05-21-2007, 07:43 PM

Algae needs two things. Light and nutrient to grow. You didn't say how long you were leaving the light on but that's the easiest first step. Don't use the light as much or block the other sources of light. 5 goldfish is also way too many for a 25 gallon so the waste load has accumulated to excessive levels after a couple weeks time feeding the thick growth. Long term you can save a lot of headache cutting back to just one goldfish in a small tank like that. Two if you stay on top of the water changes and don't mind crowding them. In the meantime while other housing arrangements are made you might try boosting that 80% water change to weekly. That and less light will help a lot in terms of algae growth. Fish growth as well but you'll need way less fish to get good growth from the fish.

On the positive side, the algae is a plant life and the more it grows, the more it helps out the water quality. It's probably the only thing saving the tank for this long.

sweetcoral81 · 05-21-2007, 08:44 PM

Hmmm, I kinda figured there were too many fish in the tank. They were really small at first. I am planning to get them a bigger tank. As for the light, that must be what the main problem is. I leave it on 24 hours a day. It's a night light for my kids. I used to turn it off during the day and then I got lazy and just started leaving it on. I will start turning it off during the day. Perhaps that will help. The tank is in a dark hallway now (it used to be in front of a window). Thanks for the suggestions!

DarkCreep · 05-23-2007, 10:13 AM

Tell your kids to man up and stop using the fish tank as a night light.

Get them a new light from Wal Mart or something, how would you like to sleep with lights on 24 hours a day?

kalamokamis · 05-23-2007, 06:16 PM

2 simple solution, talking parent talk, for my kids its a night light also, (a 55 gallon night light in there room) , but I control the light with a timer, I have it going on before they wake up for school and it turns off by 9:00 am, then it turns on aroung 8:00pm during sleep time and closes by 11pm, I have no algae growing in my tank, My second step I use an insurance I have 4 plecos cleaning around the clock , But I think the timer on the light should work wonders. I tell you the fish can give some good bedtime stories for the kids until they fall asleep, no tv required........

Crazy80 · 05-23-2007, 11:41 PM

Light timers are awesome for more than one reason we should all have them hooked up to our lights

sweetcoral81 · 05-24-2007, 05:12 PM

I like the idea of the timer - I can't believe I never thought of that. Since I posted the first post, I've been turning off the light when the sun comes up around 5:30am and turning it back on around 8:30pm. Hopefully this will help keep the problem under control. I also didn't know I needed to change the water so often so I will start doing that too.