Tank Crashed, Please Help

[Hollyweb]

About two days ago we had to move our 30 gallon that's in the living room. This tank has always been very healthy and has been established for a little over a year. In it we had several platies, a couple of mollies, 3 serpae tetra, a leopard pleco, a rainbow shark and 3 bosemani rainbows. It's been a happy tank and we've never had any problems with it other than the occasional outbreak of Ich.
 
We bought a new sofa so we had to do some moving around and the fish tank is one of the things that had to be moved. This was all done while I was at work, but the tank was emptied to about 25% full and gravel vacuumed but they didn't take the fish out. The tank was moved and then refilled with water treated with Start Right. We're not sure how or when it happened but at some point the heater either came unplugged or never got plugged back in when everything was rearranged so the water temperature in the tank dropped to about 72 degrees.
 
We thought everything was okay and the fish seemed a little bit in shock due to what we thought was the move but then they started dying off rapidly. In about an hour's time we lost all 3 serpae tetra, all 3 bosemani, 2 mollies, a couple of platies, and the rainbow shark. The rest of the fish we were able to pull out and distribute to other established tanks and then I did a water test.
 
Ammonia was fine, between 0 and 0.25ppm. The Nitrites were also fine, and pH was fine. The nitrates however, were through the roof. It's a liquid test kit and I think the nitrates were somewhere between 80 and 160 according to the color chart. Since the tank was empty we added some prime to the water and decided to let it sit for a couple of days before adding the fish back in.
 
Tonight when I got home I tested the water and the nitrates are still ridiculously high. At this point would it be best just to disassemble the tank and clean it out and start over completely or just do a 100% water change? We're assuming it was a combination of the shock of the move, with the change in water temp and the high nitrates that caused the mass die offs, but we don't know what could have caused the spike in nitrates.
 
Any advice would be welcome.

 

[Gruntle]

It's possible you may have a dead fish somewhere in the tank, decomposing (ammonia production), cycled quickly by your bacteria into nitrates.
 
Check carefully for bodies, do a 100% water change and try a dose of ammonia (your bacteria should be fine). If it cycles to 0 ammonia, 0 nitrites you should be okay to repopulate. You might also want to rinse your substrate in tank water if possible.

 

[TwoTankAmin]

A lot of the good bacteria does live in the substrate. In tanks with no live plants with roots in the substrate, the top 1/2inch is rich in bacteria. Doing a major vacuuming can turn over the substrate and kill off some of the bacteria. It can also put ammonia causing things into the water. if you did not test for ammonia and nitrite soon after, you may have missed them. All you would see is the nitrate. But nitrate need to get pretty high for a while to harm fish. When they do they tend to work in the same way as nitrite does. this means you would have noticed your fish gasping at the surface. Nitrite and nitrate poisoning cause the blood not to be able to hold oxygen and the fish suffocate in a tank even one with plenty of oxygen.
 
Next, I will never use any fish product with aloe vera. It can cause a drop in oxygen in a closed system. While this may not be an issue in a going tank not being disturbed, it may have contributed to your problem.
 
Finally, the temperature drop on top of everything else probably contributed to the stress levels and stress weakens fish. About 72 degrees implies it may have been a bit lower?
 
Do not scrub the gravel as you will only reduce the bacteria load still in it that you do want.

 

[Hollyweb]

Thanks for the suggestions
 
We did make sure we got all of the fish out of the tank so there are no dead bodies left in there, although there could be some snails, I'm not sure.
 
The tank is a planted tank but not heavily planted. I had also thought that maybe when my roommate vacuumed the gravel maybe there was gas or something trapped under it that was let lose when it was vacuumed.
 
I do think the water temp was probably lower than 72 at some point, the thermometer is one of the kind that just sticks on the tank wall and I don't know how accurate it is but the water felt cold when I dipped my fingers into it.
 
We haven't done anything else to it yet. My concern is some of the surviving platies and the betta were moved into my 20 gallon tropical tank, and now it's a bit over crowded. It's supposed to be temporary but I worry that it might cause some issues for my fish until we can get the 30 gallon going again.

 

[colleen0309]

Have you checked the nitrates in your tap water? I know in the spring, mine go up quite a bit.