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Cultivated Reef

Please help sudden cloudy water!


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I have a 34 gallon.

I use instant ocean salt mix and i tested the calcium at 360, the magnesium at 1100 and the dkh at 6.5 in my tank. I used instant ocean for 2.5 years and i decided to change my salt to the dh2o but i wanted to just dose calcium and magnesium and baking soda (not on the same days) until i used up my instant ocean salt mix and to get the calc,mag and alk similar to the dh20. I started first with the calcium dosing exactly 2 months ago today and everything was fine. I also dosed baking soda too to keep up with the alk drops if any.

I started dosing Brightwell magnesium (magnesion) exactly 6 days ago almost daily. Over 6 days i brought my magnesium level up to almost 1200. Today i woke up to find my tank completely cloudy. All the glass is covered with a light film of green algae. I thought it was just the glass but its also the water because its cloudy when i look into it top down too. My skimmer went crazy and theres some solid gunk in the collection cup whereas i would only get dark colored water at the most before.

What could have happened over night? I only have 3 small fish about 1.2 inches each. They are all fine. All my sps are fine with extended polyps. My zoas look different in that their tentacles are reaching upwards. My green star polyps are closed up but usually they are closed in the mornings just before the lights come on. My xenia and rics are normal. My dendros are extended and looking normal.

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If the water is green too then you have an algae bloom. The cause is always the same, too much light and poor water quality. Excessive light cannot only be attributed to the aquarium lighting but also intense room lighting and direct sunlight.

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yeah it looks as if my tank had a full out cycle over night!.

i dont know what could have happened. I just know that theres a lot of gunk in my skimmer now and now after 6 hours the water has cleared up and the glass has cleared up noticably as well.

This is baffling. I dont know if i should do a water change or let it be for a couple of days.

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Water change will not help an algae outbreak. Just keep skimming heavy and changing out or cleaning your filter materials often.

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Cutting down on feeding will also help. The fish will do just fine for a few days on rations.


Sounds like the skimmer is pulling most of the junk out, so all should be well in a little while.

However...my experience is that often you will exchange one algal species for another, each will persist for a little while before disappearing- just to forewarn you...




Paul @ TeamVF

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i have three fish and i hand feed 1-2 mysis each every 3-4 days and i dont let any get wasted. I also feed 1 small mysis to each of my dendro polyps once a week. I make sure the mysis are small because i know a lot of what goes in comes back out of the dendros undigested. The fish get it when it does. Other than that i dont feed my tank anything. the rest of the time the fish are eating pods. I use RO water and my tap water before it hits the RO filter has a tds reading of about 9-11. I dont know where my nutrients are coming from. I think it might be my salt.

I tested freshly mixed salt water and i couldnt read any phosphates but i think maybe there are some nitrates but its really hard to tell. My rock is 3 years old but my tank went through a move and i replaced my sand 8 months ago.

I do 10% water changes every 4-5 days.

I have 122 Liters of water in the tank and i run the tunze 9002 nano skimmer. My skimmer has always pulled out an inch of dark liquid every 2 days.

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  • 2 weeks later...

i believe something similar happened to me as well, except after one night, my monti caps bleached, my shrimps died, and some snails died. i had to move my entire rock/livestock to a hospital tank, which then go COVERED in brownish colored hairy algae. it was nasty. i just put everything back in the main tank today after waiting a few days to let my new water mix.



does ur water smell like terrible nastiness?

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