TANK OF THE DEAD.....HELP

Hi all, I’ve had tropical tanks for years and never come across this problem. Just over a year ago I set up my latest tank (only have 1 at a time) 18Gallon (80L) tank. It’s well established but over the past 3-4 months every Plec I put in the tank does after anything from 2-14 days
I’ve checked the water with several places and all same results as we expected - perfect levels etc 80.6F (27C) temperature.
We’ve got 12 Neons, 4x small (approx 1 inch length) Red tail Tetra, 6x Molly. Currently have 1 plec left (only a baby approx 1 inch) but the second died yesterday we think?
Any ideas as to why they keep dying??



i noticed a few days ago he seemed a little sluggish and swollen underneath??

Hopefully someone who knows more than me will weigh in. But the thing that jumps out at me from your post is potential overstocking? 80L is not very big. Plecos of any sort (I assume yours are bristlenose?) produce a considerable amount of waste and add a lot to the bioload of a tank. It seems as if you have quite a few fish in there, and you can get spikes of ammonia and other bad stuff that the water quality test kits won't necessarily pick up.

Here's my experience with overstocking small tanks: I had a 60L tank at one point, with cherry barbs, pygmy corys, and otos. The corys and otos would sit on the substrate, completely inactive, all day. I tested that bloody tank all the time, but the API test kit never flagged any issues. Everything that should be 0 was apparently 0. But my oto population dropped from 6 to 3 and pygmy corys from 8 to 3. Then I gave up and replaced it with a 125L tank, and the remaining corys and otos perked up. They are still with us, about a year later. Otos are still not at all active during the day, but they buzz around at night, and at least they rest on plants or glass instead of the ground. Corys now act like normal corys.

I feel like I learned the hard way that you need to be super cautious with stocking small tanks. They're not as stable as big ones, and test kits may not reliably detect spikes and fluctuations. I have one that's circa 70-80L now, but that only hourses three pencilfish and three Apistogramma borellii.

Also, Ancistrus species eat algae, but you need to supplement their diet with algae wafers and fresh veg.

Hello and welcome to the forum!

I concur with the above...Sadly, if it is a BNP, you could get by with having him in there for a couple of months at max.

Do you know if it is a BNP? Or is it a “common” pleco?

Welcome. So sorry about the losses. Been there too.

Do you've a water test kit? The API Master Test Kit will last about 800 tests so works out at great value. We need to see what's going on in the tank regarding ammonia & Nitrite & nitrate.

Do you have a GH test? This tells water hardness. While it's not the culprit the hardness/softness is an issue as you have soft water fish (tetra) mixed with hard water fish (Molly).

Without water test it's hard to know. The Plecos are usually pretty hardy fish. The Bristlenose needs a tank size 60cm/24" length by 30cm/12" width. But again this should kill your fish quickly.

Ammonia is usually the culprit so I'd recommend doing big water changes daily until you can test the water with a proper liquid kit.

Are you using any tablets or chemicals that will remove algae? Many years ago when I first started and was none the wiser I was assured by a LFS using a tablet called "No More Algae" wouldn't hurt my plecos. Seemed like they died within a few days of using it if I recall correctly. I know prob is a dumb question, just figured I would toss it out there.

TARDISROB said:

It’s well established but over the past 3-4 months every Plec I put in the tank does after anything from 2-14 days

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Out of curiosity.. when you say every plec you put in there.. Are you by chance getting your plecs from the same source? Also, how do you go about acclimating them?

I won't touch up on stocking and such (already been brought up).. but if your other fish are fine and all, and it's just the plecos having issues.. could it be a problem with the source, or the acclimation process.. ?

if you get some free time, you might call that store and see if they can get you the water parameters from the tank it came in. If it is one of the major chain pet stores, ask them if you freeze the one that passed and return it if you can get store credit.

Just spitballing really, lol sorry about all the questions from us too (don't take any of it personally) - everyone's just trying to understand the full picture to figure out what's going on, and I'm also sorry about your pleco's >.<

ReT_SqUiD said:

I was assured by a LFS using a tablet called "No More Algae" wouldn't hurt my plecos. Seemed like they died within a few days of using it

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That's good to know.

I agree with Post #6 by Koglin.

The fish might be too young and struggling at the shop.
The shop might be doing water changes on the day you get them.
The fish might have only come into the shop a day or two before you get them.

Maybe try a slightly bigger fish or get fish from a different shop.
Ask the shop when they do water changes and buy fish a day or two before they do the water change.
Ask the shop when the fish came in and don't buy fish until they have been in the shop tank for at least 1 (preferably 2) weeks.
Find out what the pH and GH of the shop tank water is and compare it to your own.