Purple algae purgatory

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Aquarium Advice Newbie
Apr 1, 2024
stl, MO
Hi! I’m new to this forum, but I’ve had 2 45 gallon aquariums for about 12 years now. Besides the occasional algae spread here and there, I haven’t had any problems keeping up with my tanks. I recently moved and ever since setting my tank back up 3 months ago, I’ve been in a losing battle with this purple/blackish algae. Partial Water changes, full decor cleanings and algae treatments aren’t helping at all. I was thinking maybe adding fresh water was only helping it grow, so I’ve tried to just clean the glass and decor and let the water be for the last month but still no luck. It always comes back fast. Any tips on how to get it out and keep it out? Attaching a photo: sorry for the cloudy water, just cleaned up the algae on the glass and stirred up the substrate a little bit while cleaning the decor. This pic is also right under the filter so lots of bubbles since the waters a tad low right now. For context: that castle is light grey and blue normally 😅


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Algae is the result of too much light combined with too many nutrients.

How big is your tank? How many fish do you have and what species?

Do you know your water parameters? ph, ammonia, nitrite and nitrate?

Is your aquarium sat in natural daylight?

How long are you keeping the aquarium lights on for?

Are you over feeding your fish?

Whats your normal water change schedule?

To control nutrients, dont overstock your aquarium with fish, dont overfeed them, add plants that consume nutrients, and keep up with your water changes.

To control light, make sure your aquarium isnt sat in direct sunlight, and keep the aquarium lights on for no more than 6 to 8 hours a day. If you dont have plants you can cut back on the lighting even more, but if you have plants you need to find a balance between enough light for healthy plant growth without too much that fuels algae growth. 6 to 8 hours a day is usually that sweet spot.

Algae will happen in aquariums where there is light and nutrients, so thats most aquariums.
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