Need your advice on pond health

Description: The pond is 1200 gallons, 3 years old, 60-70% cover.
Plants are yellowing and slow growing
No string algie but moderate flowing algie.
Water is clear to 2'
10 7-9" goldfish
20 2-3" goldfish
No bio-filter
37 gallon per min pump over waterfalls

Testing:
PH = 8-9
Nitrate = no colour change on test
Nitrite = no colour change on test

I think I have a nitrate deficiant condition.
Do I bring the PH down first or elevate the nitrate

Is there something else I should be testing for before doing anything?

What would you recommend?

Hi theponder
you should take a test for ammonia, the build up of that can cause plants to go yellow and die.

Visibilty to two feet, well have you stuck a cane down to the bottom and give it a twirl, it may well be algea growth that is blocking the view, this would also count for the other plants being starved of of nitrate, algea sucks it up faster than the plants can.

Solutions for low nitrite can to add a nitrifiying filter, only a small one would be need, it turn the fish waste from harmful chemicals to nitate, feeding your plants, but, feeding algea too, another way is to test the nitrate content of your tap water, some areas it can be high in nitrate which is harmless to us, but good to the plants, so a bit of a water change to your pond would be of benifit too.

So check for algea first, if pressent remove as much as you possibly can, it may take you a few weeks to get on top of it, but once your plants are back to full health they will help starve it, low direct sun light on the pond will also help keep it down.
Check for ammonia, high levels in the water act as a poison to some water plants, fish will suffer long term affects too, best way and fastest way to reduce ammonia is to change water about a quater of pond volume every two days untill the levels of ammonia have dropped, but htis is only needed if the levels are high.

PH levels are best if kept at 7.5 that is perfect, 8.00 is not too bad, but 9.00 you should take action to reduce this too, again a one of partiel water change will help that, then add a good handfull of aquatic salt, this will add mineral and help to combat ammonia, and PH and algea growth.

Another thing to check is the bottom of your pond, after three years the build up of dead leaves and plant particles will be high, try to clean up as much as possible, this too will help with all the things listed above, and gentle scoop of the bottom with a net to remove all winter debris is a good maintenace for the spring and will go a long way to preventing further problems in summer months.

I hope this is of help and not put you or other readers of haveing a pond, it sounds like hard work, but the work can be just a few minutes and save you a lot of time in the long run, good luck.

Thanks AJC for your suggestions. I have made a check list and I am working thru it now.

Our Garden Sancuary: http://www.mhelm.com

Hi Theponder, just checked out the link, great pond like that waterfall, very nice.