Very high nitrate levels

Question
I have a 55 Ga. tank with about 30 African cichlids.The tank has been set up for about 4 months now with some live, thriving, plants, I have set it up with a crushed coral substrate, and most of the ornamentation is natural. (Texas holy rock, Madagascar driftwood and live plants)I have read that you shouldn't mix different lake African cichlids but I have and temperament speeking, The tank is pretty calm. My levels all stay pretty constant with the pH @8.0, alkalinity @180, chlorine at 0,hardness @150, nitrite@.5, ammonia @ 0, and nitrate @180. To my knowledge everything but the nitrate levels are ok, and because of the nitrate levels I do 25% water changes 2-3 times a week. The fish appear to be quite healthy and happy. I almost always have female holding fry and have raised 12 fry since the tank setup. I have been told that if the fish are breeding, and the fry are living... don't worry about it. what, if anything, should I do?

Answer
Hi Jeff
Saw your question in our question pool.

Yep, those nitrates are high.

First, what kind of test kit are you using?  
The liquid dropper kits are better and more accurate then the dipstick kinds.  If you're using a dipstick, try the liquid dropper.

You really want the nitrite readings to be 0 ppm as well.  Some fish can tolerate a small amount of nitrites, but it's always recommend to keep them at 0 ppm.

Next, test your tap water for nitrates.  Well water commonly has some nitrates present in it-usually from run off.  But, usually not that high.  Worth it to try testing it anyway to rule that out as the source.

And, finally, awhile back while considering setting up a saltwater tank, I had read that crushed coral is not a good idea as  a substrate-because it's a nitrate factory.  All those tiny shells make it very difficult to effectively clean the substrate.  You're better off putting it in a mesh filter media bag and hanging it from or in the filter.  So, if all the other stuff checks out ok, might be a good idea to consider a substrate change.

Hope that helps and good luck!

Christy