Filter suggestions for 30g tank?

We started keeping fish last winter, and have had our 30g tank set up since ~ May. As many of you know, we’ve had a string of health issues in the tank. I think our filter isn’t working very well; it spits small detritus into the tank even right after cleaning, and the tank starts looking like it needs changing every 48h or so. Stats:

Ammonia 0
Nitrite 0
Nitrate between 5 and 20
pH 7.8
GH 180
TopFin hang-inside waterfall type filter, sized for 30-40g tanks
Bubble wall
Stocking: 3 cories, 7 guppies (hoping for more cories and a BN pleco, but can’t until we can keep the tank healthy), 1 sword plant, 1 ailing Java fern

We feed a small pinch of flakes (3-6 flakes, crunched up) and 3 small pieces of algae tablet most days, with small fragments of rotating frozen mixes every few days (mainly brine shrimp based as the guppies are really too small to deal with bloodworms).

What kind of filter would you-all recommend for this kind of community tank? Our one limitation is that we can’t hang anything outside the tank; it lives in a bookshelf with just an inch or two of clearance on the sides and back.

An aquaclear hob would be perfect for this tank

It would indeed, if we had the space to hang it. We only have about 2” clearance on sides and back.

I actually have a Silenstream in a box that we bought, doesn’t fit, and can’t return. If anyone is in the US and could use it, message me .

Familyfishny said:

It would indeed, if we had the space to hang it. We only have about 2” clearance on sides and back.

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True. The aquaclear is about 3.5 inches on the back.

Final report: I wound up looking at the Tidal series, the Top Fin Pro Series, and the Marineland Penguin series. I wanted to size up a little given the problems I’ve had, and the only one that fit the narrow gap between the tank and the wall was the Penguin. I installed it a couple days ago, and it is definitely an improvement over the last filter with much clearer water and fewer particulates. The current is a little strong for our guppies, so I added a water bottle baffle, and hope to find something to screen the intake to protect any fry. Fingers crossed it will improve our tank health.