Immidiate Help~ Ammonia disaster... gravel to sand conversion failure ??

Hi there~~

I need you xpert's advice and help for my tank asap~!

I have a sting ray goin into my 150 gal (140??), and I had 2~2.5" gravels in it be4. Becoz everyone says gravels may hurt the ray, I decide to replace it w/ sand. Then, after I took out all my gravels for about 2 hrs (Still bare bottom), I noticed that my ammonia indicator shows alert . I did a immidiate ammonia test, and it indicated that the ammonia is d@mn high. My tank was running one wet/dry system (1250 gal/hr), one Marineland 350 (400??) filter and Unknown Japan hang over filter w/ extra ceramics in the filter. I didnt hab ammonia problem be4, and I realli believed that I should be fine w/ even bare bottom. need your suggestion on this plz...

Now, I put another Rena XP3 (for 175gal) on, which means i am running 4 filters .... Ammonia reading has lowered down a bit, however it's still high... What do you guys think? Any suggestion and help will be very appreciated....

Thank you so much~~~

I forgot to mention... I am still having bare bottom, so maybe that is the reason ?? not enough surface area for the bacteria ??
I have a lot of ammonia clear chips in there ( for at least 330 gal), it was in there be4 everything happened...

oh ya~~~ and i had just did water change 2 days be4 all these.... which means... it's not water change problem, rite ??

It's already 2 days.... I am very scared, and my ray is in holding... I must have the problem solved immidiately, someone help me plzzzzz~~~!!!!

Also, can you suggest me wut kinda sand to buy ?? I see there are black sand in petmart, i like those.... BUT~ how do i know wut kinda sand is good for ray, how do i tell.....?

Thank you for all ur responds... thanks..

Wut is " Prime" ?? is it a brand? a chemical? would like to tell me more detail plz??

Here is the update:
I did another 50% water change yesterday, which just like wut you guys suggested...Added one bottle of Cycler, and nothing changed... this is so strange...

Wut I have done now...

1x 30% w/c on 2/16 (5 days ago)
1x 30~40% w/c on 2/18 (rite after taking out gravels)
1x 50% w/c on 2/20 (Yesterday)

Running:

1x Wet/Dry sump w/ a lot of Bio ball, and Ammonia clear chips ( 4x 110 gal bag)
1x Rena XP3 (175gal) w/ my old gravels in it and ceramic
1x Marineland 350 w/ ceramics
1x Japanese top filter (40 gal) w/ ceramic
1x Power head (replace filter w/ ceramic)
2x heater
2x air pump

Add:

4x 110 gal Aqua Clear Ammo chip
2x Carbon bag
2x Large bottle Cycler
1x Chemi-pure
5x pills of ammonia remover...
1x huge bag of my old gravels in washing net (i just put it bak yesterday, hope it works)
A lot of water conditioner (cant track)

PH 6.8, I heard ray likes low ph.....
and every other readings go up and down... i cant track... I will measure again once i got home...

Oh ya, just for reference.... all my fish seem doin alrite (4 fish) ..... except the arowana looks a lit stressed and nervous (jump a lot) .... i guess it caused either by too much actions recently or bad water..... i am not sure...
More feedback PLZ~~ Thank you....

Steve at petworld test my water... he didnt test the ammonia... but he said my nitrite is safe... so he believes that my water should be fine... However, his kit shows that i hab high nitrate, which is very weird ( Nitrate should usually be removed by water change) .... with all the water change I did.. plus filters and chemical.... i am confused abt the result. I see most ppl on the forum dont have this problem when they convert from gravels to bare bottom or sand......

i tested it few hrs ago.... the ammonia does come down .... i cant realli tell from the kit... i guess it's around 0~0.25 , however this result is measured after i dump in a lot of AmQuel (Ammo remover).... Therefore, i am not sure abt the water stability.... I will measure again once i got home.....
now, ph 6.8 , Ammo ~0.15, Nitrite 0~1 ppm, Nitrate 250 ppm....

I will bring my water to another lfs tomorrow ... i will keep u guys updated...

For additional reference, I measured the water quality of the tab water i used.... i suspected its quality.... I heard OC water contains high Ammo in it.... i dunno....

the reason i suspected that is... you see i have no gravels now, which means i hab nothing to trap waste, I already did 3 times water change, which means i have almost replace all my old water w/ new water. Also, I stopped feeding my fish ( only 4 ) for 5 days already.... i know fish produce waste, however i doubt it will affect that much....

After I tested it... omg~~ the ammonia for tab water is 1 ~2.5 ppm !!!!

Guys~ this is fxxking scary... for me always believe w/c help the water quality..... my lit testin experiment completely overthrow this theory....

Maybe, i should create a new post abt this, and share this info to all members here.....