Fish Disappearing-ideas?

I had 3 golden topminnows, 10 glowlight danios, 2 otocinclus and 5 peacock gudgeons in my 29 gallon. 5 glowlight danios and 1 gudgeon went missing. I blamed the topminnows. Moved them and put in a pearl gourami from a different tank. A few weeks passed. Nothing happened. Two days ago 1 more gudgeon disappeared. Yesterday another gudgeon disappeared. No bodies, no other fish acting any differently. Danios still chasing each other and gourami still hovering like a fishy drone. Two remaining gudgeons still doing gudgeon things. Otos still munching diatoms. Before yesterday's water change my numbers were as follows- 0,0,20 (nitrates in tap), 77 degrees and 8.0 pH. My filter is a large corner filter with no room for fish to get in. There's a gap in my lid but no fish bodies have been found. I moved everything in the tank and found nothing. I use a siphon but I keep it kinked while vacuuming so nothing gets past the tube if it enters after the first time the danios disappeared. That time it was possible someone got sucked up and removed by accident because I walked away for a minute with the siphon in so I've been really paranoid ever since. Is it possible my danios are harassing my gudgeons to death or my gourami is eating the ones that are left? I'm trying to stock this tank, not decimate it. And I bought five gudgeons to hopefully breed, so now I'm out of luck. Any ideas?

 

I always had really terrible luck with Gouramis, maybe move him out and see what happens.

 

No chance the pearl gourami ate them. They are probably one of the most non-aggressive fish I've seen.
I guess anything is possible, but I highly doubt it is the culprit. Do you have a cat or dog that could eat the fish if they jump out?

 

No chance the pearl gourami ate them. They are probably one of the most non-aggressive fish I've seen.
I guess anything is possible, but I highly doubt it is the culprit. Do you have a cat or dog that could eat the fish if they jump out?

I do have cats and dogs but this particular tank is out of their reach from baby gates for our toddler. Cats don't jump the gates because they're super old and there is nothing in that area of interest to them. The first six fish that went missing either got eaten by the now relocated topminnows or got sucked out during a negligent moment in a water change. But the remaining fish that got gone are definitely making me wonder about aliens. If they died and were eaten I could understand the bodies being gone, but none of these fish were sick. I would think the otos would be the first target since they're mostly just hanging out at any given moment. I'm heavily shrugging my shoulders.

 

Anders believe it or not I had a large Pearl that was eating my Neons once upon a time. I really do just have terrible luck with them lol. All gouramis really. I haven’t tried keeping one in years despite loving how they look. But you are probably right. If it’s not that, it could be that they died and were consumed postmortem before you saw. OP- If this is happening around water change times (since you mentioned the siphoning and the few weeks between) my only other thought is you could be having ph swings if you aren’t using a stabilizer in your water changes that might be causing probs. You could try setting up a nest cam on your tank and trying to pinpoint when exactly things go poof. I wish you good luck!

 

Anders believe it or not I had a large Pearl that was eating my Neons once upon a time. I really do just have terrible luck with them lol. All gouramis really. I haven’t tried keeping one in years despite loving how they look. But you are probably right. If it’s not that, it could be that they died and were consumed postmortem before you saw. OP- If this is happening around water change times (since you mentioned the siphoning and the few weeks between) my only other thought is you could be having ph swings if you aren’t using a stabilizer in your water changes that might be causing probs. You could try setting up a nest cam on your tank and trying to pinpoint when exactly things go poof. I wish you good luck!

So no fish disappeared for a few weeks but I still did water changes, so I don't think it was a pH swing. I do 50% on all my tanks every week barring some major time crunch or something. And I did consider the pH thing, so I did tests on source and tank this week and it was 8.0 on both (well water). I figured they were dying and getting skeletonized before I could find the bodies.
The weird thing is that your wishes for good luck must have worked because this morning there are three gudgeons again! This leads me to believe that aliens must have returned it last night after lights out. . I don't know how that fish was hiding. I moved every single thing in the tank and watched the tank for over an hour. My husband was starting to get concerned about me. He thought I was losing it. He may be right anyway but at least I have three fish again!
Thanks everyone for your help.

 

That's happened to me before. A fish was hiding inside of a rock and I thought it just vanished, but it turned up days later haha. I hope you have no more losses! Gudgeons are awesome fish. I have two myself currently.

 

Set up a hidden video camera in your tank room, train it on the tank but include the floor around the tank. Turn it on and carry on as normal for a few weeks and just check the footage and you will soon find out who the culprit(s) will be....you might be surprised what goes on when you have your back turned or at night....you say that your cats are getting on a bit in years but every cat, no matter how old, sees fish and thinks food and lets not fool ourselves, cats can be seriously sneaky when they want to be....

Catch the action on camera and you'll find out what those fish & other animals are getting up to.....and check your walls for holes too cos dropped fishfood can attract life's furry invaders too and they can climb if hungry enough. A friend of mine had a similar issue to yours, set up a camera for a few weeks and caught a rat not only raiding the fishfood but also raiding the fish tank too....count nothing out.

 

Well that’s terrific they reappeared! I have had that extended hiding thing happen in my saltwater tanks in the past but never in my fresh! Sounds like you have a setup they are really enjoying Good to see good news in this thread!