New Guppy Behavior? Is it normal?

Hi all, sorry if I seem to be posting too much. I ended up returning the females and got 3 male cobra guppies instead. Just wanted to know if it's normal for the guppies to stay at the top of the tank? They aren't motionless, but they do swim around a lot but don't go deeper, always staying near the surface.

The tank is cycled, and the water is heated at 78F.
Ammonia and nitrites are at 0, and nitrates are 10 ppm. pH is at 7.5 and hardness is at 180 kH. There is a filter and a bubbler in the tank.

If your nitrates are 100 ppm your fish are going to die. you need to keep nitrates under 40ppm or your fish will die. You need to do water changes to bring that down.

something is not right with your water. Cycling issues most likely


image source

Actually, nitrate should be kept below 20 ppm.

@HalfTailedOwner - what is the nitrate reading of your tap water? Some places allow as much as 50 ppm in drinking water and if you are unlucky enough to have nitrate this high, it is impossible to get the tank nitrate below this by water changes alone.
However, 100 ppm nitrate is double this maximum allowed in tap water, so there is a lot being made in your tank. How often and how large are your water changes? I know 3 guppies is not many (unless there are also other fish in the tank) but if the tank is small and water changes not large/frequent enough, nitrate will still build up.
The usual causes of high nitrate are:
inadequate tank maintenance - water changes, substrate cleaning and filter cleaning
too many fish
over feeding

As above, the nitrate reading is too high.
Do a 75% water change each day that the reading is over 20ppm, add oxygen via an air stone and pump, and reduce feeding. The guppies should then swim around the tank more.
Does your tap water have nitrates? If so, how much?

EDIT Sorry, post crossed with Essjays.

@Naughts @essjay @AmandaN
Wait!! Sorry everyone I didn't notice I made a typo, it was supposed to be 10 ppm until i read the comments but the reading is what looks like 10 ppm, not 100 ppm. Here's a picture from the most recent testing (yesterday)

That's a relief

Are you still worried about the guppies behaviour?

@Naughts @essjay

There's a problem though... two of the three guppies we got suddenly died. I don't know what happened, and I ran the water testing kits again -- all of them are normal.

0 ppm ammonia and 0 ppm nitrates with now 20 ppm nitrates. That isn't lethal but it's barely been a day and they suddenly died since I got them from PetCo. It's the only place that's close by; there was a lfs before but it closed down. Are the fish dying from shock? I'm not sure about that though, since I do acclimate the fish for at least 30 minutes before letting them inside the tank. Is something going on before I buy them? What exactly should I do about the water? What should I do with the guppy that's left?

Your water is fine, maybe Petco had poor water or sold them before a quarantine .
Sorry for your loss.

Naughts said:

Your water is fine, maybe Petco had poor water or sold them before a quarantine .
Sorry for your loss.

Click to expand...

Aw man.
Not sure if I'm gonna get another guppy then. What can I do about the remaining guppy though? Will it be fine without anyone else?

He will be ok on his own.
It might be an idea to see if your area has an aquatic society. You could get fish from them in the absence of a lfs.