Question
Albert:
I had a severe case of diatoms and took your advise using a silicate-removing compound and the advice of a local fish store in turning off the lights for three days and doing a 25% water change. It worked as I got rid of the diatoms but now I have extremly green water and alot of green algae. I do not know what to do.
I have lowered my lighting to 4 hours per day instead of 12. The tank's parameters are as follows:
- My temp is between 76-80 F
- My salinity is 1.019 @ 75 F
- My PH is 8.3
- My ammonia is 0.0
- My nitrites are 0.0
- My nitrates are less than 10.00 ppm
- My phosphates are 0.2 ppm
- And everything else is fine except for this cloudy green water I have.
I have been doing weekly water changes at 10% too instead of my normal monthly 25% change. It seemed like I had a severe case of diatoms and when that cleared up I got green water I suppose algae? And my phosphates are not that high. What do you suggest doing? The local store says to leave the lights off again and do a water change.
I have live rock and am concerned with it having not enough light. I know everyone has their own opinions but I want my clear water back and it is getting extremly expensive using all of these chemicals, and they seem to do nothing. I have noticed that the redox is making my protein skimmer work more.
I always vacuum with a Magnum once a week and have hardly any detritis material. It is like everything is suspended in my water. I use RO water, always.
I have a wet/dry, skimmer, and a 350 Magnum for all my chemicals. Please help me out if you can.
Answer
Dear Hobbyist :
I don't want to imply that you got wrong information, but leaving the lights off is not my favorite way of getting rid of algae. What happens is that the algae die for lack of light and then decompose and pollute your water even more. When you then switch the lights back on, suddenly, because of all the nutrients, there will be more algae appearing in a real short period of time, sometimes as short as overnight. Depending on the nutrients you may see both brown and green undesirable algae appear. This is a real common occurence. Unfortunately, this recommendation is often made and hobbyists are at a loss to understand why algae reappear (sometimes to a larger degree than before).
That seems to be exactly what happened in your tank. I would not switch the lights off but I would do the water changes and treat the tank with both silicate and phosphate removing compounds, but you are going to have to do so several times in a row to remove all the excess algae nutrients that are now present.
The treatment method I recommend and that will give you the results you are looking for is as follows:
- use the recommended dose of the product you choose and leave it in the canister for 4 days
- siphon out any algae that die off so they cannot break down and pollute your tank
- after 4 days replace the compounds and leave them for four days again
- siphon anything that dies or discolors out
- do this for 3 or 4 times in a row and you should have real low silicate and phosphate levels, low enough so the algae do not regrow.
- note that the the silicates will be at a real low level before the phosphates will
- to ensure that the PO4 is low, it would help to have a phosphate test (ortho-phosphate).
You are correct in thinking that leaving the lights off for too long is not going to help your live rock at all, and is going to cause more die-off which, in turn, pollutes the tank even more and makes even more algae grow. The treatment above is described in my book Ten Easy Steps, but since I gave you the way to go there is no need to buy it.
As I said you may, and probably will, need to do this a couple of times. The number depends on the levels of PO4 and silicate/silicic acid in the tank.
After you have completed the treatments make sure you keep some of the compounds in the canister (now they will last much much longer) to prevent the algae nutrients from rising again.
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