I would say give it another 2-3 weeks before everything goes to normal...It may go faster...Rays release a lot of bio load and I don't think ur tank was fully cycled with just a few small fish..
At what point.t is it dangerous for the rays? How much of a water change shoulder I do everyday? What bacteria does everyone suggest for this tank. I don't want to spend a fortion but if there is something I can add let me know. Remember its 300 gallons.
I would add the bio balls even if they are going to be fully submerged, can't hurt anything and will probably help some. dr_sudz has point about the water changes depleting the bacteria, but given the ammonia and nitrite levels I would keep them going if it was me. Can't say how long it will take to cycle from here, but the fact that you have both ammonia and nitrite does mean its getting there. You need some bacteria in a bottle to move things along quicker.
Are the rays eating? You might want to stop feeding them till you get things under control, the more they eat the more waste they put out and the worse the water is going to get.
Anything above .25 on ammonia and nitrite should be considered stressful to a ray, ideally you want both readings at 0. At your current levels these readings are very dangerous for your rays, the prime you have been adding is probably all thats keeping them alive.
This is the product i would be highly recomending, remember this is not the normal aquarium size, your are dealing with a small glass pond here. http://www.pondworksetc.com/microbelift17.htm I would say that if the rays are acting normal and not stressed then the prime is probly doing its job at nutralizing the ammonia and nitrites, but I would get that bacteria in there as soon as possible. I am still going to say that I am weary with the whole water changes everyday/couple times a day. I would use the prime 3 days then water change about 50... Until the bacteria has stabilized
I just did a water change of about 20% I will test the water in the morning. I will try to do small constant water changes of about 20% each day for the next few days. I will then add bacteria once the levels have gone back to sake levels. I like the price of microblift but there is no where local that has it. I will try a pond store tomorrow. If nothing else I will just stick with prime. How does that sound? I don't want to loose my guys. They look really cool
The water changes help but it won't be enough to drive down the levels, only bacteria will do that. I am not familiar with microblift, but if its like stability you will have to do daily doses of it for a while. When I am cycling a tank or pond I remove the water for the daily water change and then add the bacteria while its refilling.
I don't know about the microblift, with stability you would need to dose it for 1 week, you would need about 750ml I believe, cost around $25 from amazon for a 500ml and 250ml bottle.
if your going to add anything to your sump submerged, add ceramic rings. also if you have any other cycled filters running right now you can take out the sponges or media and ring it out or place in your sump. youl bump your BB colony by a ton. youl be cycled in no time. make sure you keep testing.