Frustrating day in fishkeeping

[meadeam]

I started a new tank a few weeks ago.  It's a 20 long in which I'll be experimenting with blackwater.  I started it up with pre-cycled media including bio-rings, course sponge, fine sponge, and because I like to run air in all of my tanks regardless of filtration, an ACO nano sponge filter.  The rings and sponge I loaded into a newly purchased Oase Bioplus thermo.  I admit to being a sucker for clever design, and the all-in-oneness of this particular filter. 

Residents include 6 mid-size julli cories, and a mixed batch of a dozen neons and green neons.  It had crossed my mind that a small fish could get behind the Bioplus filter, but I think I liked the design so much and wanted it to work so badly that I ignored that voice.  I hadn't read any reviews that included fish getting stuck behind the filter, but I may have been unconsciously selective in my reading as well.  

It's been a couple weeks that the tank has been running.  The cories have been glass surfing a lot as cories sometimes do in a new tank.  I'd been in the habit of counting fish each time I walk past (tank is in the dining/kitchen) and this morning there weren't enough fish.  I got the flashlight and started looking closer and sure enough to my horror I saw two cories trapped behind the filter.  I quickly and carefully pulled the filter to release them.  A trapped neon emerged as well.  I cursed myself for wanting that filter to work so badly that I ignored an obvious design flaw (or the directions, as I rarely RTFM).

As of now the cories are all swimming, and the neon is probably not going to make it.  Each time I am sure he is dead and I approach with the net, he starts swimming again.  I submerged the cursed filter in a snail tank to keep the media alive while I decide what to do.  In the 20 Long I removed it from I have the nano sponge that has always been there, and a small sponge that had been running in another tank for several weeks.  I know this probably isn't enough, and the tank will re-cycle.  I have a cheapo HOB that I could load with the media from the from the evil fish killing bioplus while I decide what the ultimate solution is.  For heat in the 20 Long (the heater left with the cursed filter) I happen to have an ACO heater I put straight in.

This may mark my switch to air-driven filtration exclusively.  I have ACO sponges running as secondary in every tank anyway, so I'd just add another to each, or perhaps upsize the sponges as well.   

[PineSong]

Ouch! That is disappointing, though good work that your habit of counting them allowed you to catch the problem before it did even more damage. I hope you can figure out a solution--frustrating to have equipment you don't feel comfy using.

[meadeam]

It is disappointing to have spent money on a filter that I now know cannot be used with fry, or smaller nano fish.  I think some full-grown smaller fish would be ok.  I could  stuff the back of the filter with filter floss, but I think that would impede the intended flow considering the internal heater.   It is a shame because I do like the design of the filter.   When I have some larger fish in a tank that will never contain fry, shrimp, or small fish I may be able to use it again.

[Fishoutawater]

Have you got a sponge on the intake? That might be all you need.

[meadeam]

On 10/30/2022 at 5:57 PM, Fishoutawater said:

Have you got a sponge on the intake? That might be all you need.

There is no intake ala HOB or canister.  It's an internal filter that fits tight in the corner, but not so tight that a small fish can't wriggle between the filter and the glass.  It's really very thin clearance; maybe a few millimeters.  It is Seemingly too tight for anything small enough to get in without being able to get out.  But fish find a way to to get stuck.  

Photo is not my tank, but another user illustrating the problem.