Help! Climbing nitrites

When I did the last water change/test (test before change) I saw nitrites,
which had been at zero for nearly two months, at 0.5 ppm. This was
Saturday. I thought that maybe the biofilter had been not as effective
because the water was colder than previously (about 68) so I got a heater
and worked the tank up to about 72. Today, I checked again and we're now at
1 ppm! Also the water is rather cloudy. Finally, I'm also seeing ammonia
now.

Parameters:

Ammonia: 0.25 ppm
Nitrite: 1 ppm
Nitrate: 20 ppm
pH: 7.8
dkH: 5
kGH: 11

Tank is a 29 gallon, still with two comets: Hoshi at 5" (including tail).
Mika-chan at 3"
Two HOB filters. A Top Fin at about 150 gph and a Penguin BioWheel 150 (150
gph). Both have two cartridges in place and a filterfoam prefilter on the
uptake tube.

Green Dust algae that has been growing on the gravel for some time has gone
from green to a grayish color.

Help?

BTW, I plan to get a 55 when I get paid at the end of the month and the
Goldfish will be moving there--with the 29 converted for tropicals.


--
David L. Burkhead "Dum Vivimus Vivamus"
"While we live, let us live."
My webcomic Cold Servings
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Updates Wednesdays