Algae problems

Question
Please bare with me, I am new to the fish world. I live in Florida and keep a 75 gallon tank outside on my covered deck. The tank has about six Koi 3" to 4" each and two large goldfish. I like to keep the koi in this tank until they grow large enough to put out in my Koi pond. The problem is I can not seem to get clear water in this tank. It is green. There are no live plants, I use Jungle NO More Algae, 10 tablet twice a week and get almost clear water for about one afternoon and by the next morning it is getting green again.when I do a 30 percent water change it stay clear about one whole day.  There is no direct sunlight on this tank however it is always bright and sunny outside. I love this tank on my deck it, is where I spent most of my time, can you offer any suggestion. Thank you for listening.  Betty

Answer
Hi Betty
That's good you have a koi pond set up for them.  I had a small pond I kept under my covered lanai when I lived down there.  Had no problems with algae in that pond at all.  

As you've found out, those algae removing products don't work.  So don't mess with them anymore.  What's your nitrates reading in the tank?  If you don't have a test kit, I'd strongly suggest buying one.  The dropper test kits are much better and more accurate then the dip stick ones.  High nitrates, high phosphates, can cause algae blooms.  Also, overfeeding can as well.  So, not sure on what you're doing with the tank, here's what I usually recommend:
Do weekly water changes, vacuuming the gravel/substrate, change out about 25%, with your tank of koi and goldfish, I'd go a bit higher around 35-40% once a week.  Cut back on the feedings to once a day, and even skip a day or two during the week.  Make sure you net out any uneaten food after 5 minutes-though usually not a problem with goldies and koi :)  Also, with that water test kit, check your tap water for nitrates.  That does happen on occasion, even with well water.  Another thing you could do, not sure what kind of filtration you have running on the tank, I'm going to assume you have a hob(hang on the back) fitler on there.  Check into getting a canister filter to add on there as well.  All the brands I can think of work great, I have several different brands.  Some people prefer one over another.  They're a bit more money, but definitely worth it with larger tanks.  All my 55 and over tanks I have one along with a hob filter.  You can't over filtrate a tank, and that may help as well with the increased filtration and surface agitation of the water.  PLus the canisters are great, there's enough room to add any filter media in there.  Hopefully some of those suggestions will help.  

For now, do a water change, then you can try a total blackout.  I've never tried this, but have heard others did with great results.  Completely cover the tank with a blanket.  Don't let any light get in(the smallest amount of light is all algae needs to grow).  Don't feed the fish, don't look at them, nothing for about 4 days.  The lack of light is supposed to kill off the algae.

Let me know if any of those worked for you!  Good luck!

Christy