green water in fish tank

Question
i have changed my water twice in two months and it still stays green but it is just the water and not the tank the glass is clean and all i have in the is one plecostamus have used algae destroyer and then that is when 70 dollars worth of fish started dying  THANKS FOR ANY HELP STEVEN

Answer
Hi Steven
I'm not sure if you mean you completely changed all of the water twice or if you only did 2 partial water changes in 2 months.  So...you don't ever really want to do a complete water change.  It's stressful for the fish.  And, if you meant you only did 2 partial water changes, you need to do more.  I usually recommend vacuuming the gravel good and changing out at least 25% of the water once a week-depending on how the tank is stocked(or overstocked).  

My usually recommendations for green cloudy water, not to leave the light on in the tank for more then 8 hours with no live plants in the tank, or not more then 10-12 hours if there is live plants.

Is the tank receiving direct sunlight from a window?  If so, consider moving the tank, or using a curtain or blind on the window during sun light hours.  

Don't overfeed the fish!!  Only feed what the fish will eat in about 5 minutes, then syphon out the rest of the uneaten food.  Leftover food contributes to high nitrates & phosphates-which algae loves.  

Do the frequent water changes, what I recommended above.  As I just mentioned, leftover food and waste that accumulates in the gravel/substrate contributes to the high nitrates.  

If you're tank is over 10 gallons, like 20+ gallons, consider adding another filter on the tank.  All my tanks over 15 gallons, I run 2 filters on.  The extra filtration doesn't hurt, helps filter the water and agitate the surface better, and if one breaks-you have a back up filter already running.  

Also try checking your water source.  Especially in well water, there's a possibility there's nitrates in the water source.  Use your test kit to test your tanks water parameters-ammonia, nitrites, and nitrates, and also check the nitrates in your water source.

Try those, give it a week or so and see if there's an improvement.  May not totally clear up that quickly, but see if it helps.  One thing I forgot, you can try a total black out.  I've never done it, but have heard from others that it works....completely cover the tank with a blanket, don't let any light in AT ALL(no peeking either)!  Keep it this way for about 3-4 days, and DO NOT feed the fish during this time(he'll be fine).  Algae only needs the weeist amount of light to grow/survive, so that's why they say not to look and see what's going on.  The lack of light should kill off the algae, do a water change.  Then try the above mentioned list of stuff to try.  Stay away from the chemicals, they don't work at all....What may have happened with your dying, a lot of those products consume the oxygen in the water, and the fish probably couldn't handle it.  

Hope that helps and good luck!  Let me know how it goes!!

Christy