Questions/mystery about new small pond

I just setup a 100 gallon pond in my back yard and I have a couple questions and one mystery.

1. I'm using a 633gph pump to feed a pressurized canister filter filled with lava rocks and a course filter pad giving ~6 turnovers per hour. I'm used to saltwater tanks where more turnover is better. Is this turnover too much for bio filtration to work well in my pond?

2. Would covering the bottom with gravel or lava-rocks be a good idea or not? Right now there is no substrate

3. I used water conditioner, de-chlorinator, and bacteria. Then stocked the pond with 10 1" feeder goldfish. Aeration is sufficient. I expected to lose a few as the pond established and I have so far lost 4. Here's the weird thing, I tested the water both myself and at lfs and there were no traces of ammonia, nitrite, or nitrate. The water was only a little acidic, probably from the lava rocks. I've fed several times as well. Question is, how could there be no nitrate if ammonia and nitrate are at zero ? And Whats killing the fish?

bumwrok

It's normal to lose about 40-60% of feeder goldfish ( I worked at a LFS). Your levels maybe fine and you can still lose fish. Unless you want to add to your work load don't add rocks. If you do use gravel stir it often and use 3/4 inch marble chips or river rock. You should be fine with your filters if you have that many goldfish. Good luck, Gail

Agree with richdeer3. Yes, more water turnover is better and your filters will do fine. Covering the bottom is OK if you really want to but un-necessary. Makes it a lot harder to clean and doesn't benefit the fish any. Like richdeer3 said, losing 1/2ish of your "feeders" is normal and nothing to worry about. Congrats on your new pond.

The only time that I would recommend it as some kind of benefit would be if you, like most, have an algae problem. Gravel, small river rock, etc. in the bottom of a pond gives more places for the beneficial bacteria that work on algae to live. Other than that is purely optional.

If you do use gravel than I would recommend the 3/4 inch marble landscape chips or large river rock. After years of fighting with pea gravel I took it out of all but my 20 gallon guppies and swordtails. The pond is much cleaner and easier to maintain.

yeah, and i forgot, wash it really good first. If it is larger like 3/4 inch it definitely is much easier to keep clean.