Mysterious Tank Conditions Causing Fish Stress :(

Hello Everybody!

I'm new to the forum so bear with me here because this will require quite an explanation. I have a bit of a mystery that I need help solving before it starts killing my tank inhabitants. My 20-gallon long tank setup seems to be stressing any inhabitant that I put into it and I'm having trouble identifying why.

Here's the backstory:
I recently purchased said 20 gallon long with the intent of growing a colony of cherry shrimp. The tank was set up with an Aqueon Quiet-Flow 30 (hang on back filter meant for tanks up to 45 gallons - this used to be the filter for my larger aquarium before I upgraded to a canister filter), a submersible heater, a glass hood, and an LED strip. I successfully cycled the tank with one small fantail goldfish whom I later moved out to my bigger tank.

I immediately replaced the fantail with 30 cherry shrimp, all of whom died one-by-one over the course of the next month. The only reasonable explanations I have been able to come up with for my inadvertent shrimp genocide are either that (1) I couldn't keep my pH low enough for them - NH4 and NO2 stayed at consistent 0 ppm and NO3 was kept below 10 ppm with frequent 10% water changes for that entire month while I never got a pH below 7; or (2) the weather started to get pretty warm during the day during that month - the tank was experiencing 3-4 degree temperature swings from morning to evening and that could have been even worse during the day when I'm not home.

Anywho, the shrimp all died and I've moved on from my aspirations to house them in that tank. Between the hardness of my tap water and the temperature swings in my kitchen, it wasn't meant to be.

My Current Conundrum:
About two weeks after the last shrimp death, I performed a 20% water change, went and bought a small oranda goldfish and a mystery snail, and introduced them to the tank. Water parameters at the time were NH4=0, NO2=0, NO3=5ppm, pH=7.6, 76.1 F. The oranda showed pretty immediate signs of stress - he was gulping rapidly and darting around (I had temperature acclimated him by floating his bag in the tank for 20 minutes prior). He didn't calm down at all until we turned off the tank lights and left the room, at which point he came to rest hovering just above the sand in a hide spot behind a fake log. The snail pretty immediately dug a large hole in the sand and quasi-buried itself and did not come out to walk around until the evening.

We kept the tank lights off until the morning and the oranda didn't start darting around when they came back on but he stayed very lethargic and close to the sand. After attempting water and filter media changes to no avail, we eventually moved him out of the tank into a larger one where he immediately returned to normal, happy goldfish behavior (swimming around and foraging for food in the sand). The snail was left in the tank because there is another mystery snail in my larger tank (I have no idea what sex my two snails are and would prefer not to risk having snail babies) and while it consistently digs a hole and just sits dormant during the day, it moves every night.

We have since done a comprehensive clean of everything in the tank with the exception of the filter (since it just got a new media cartridge I was afraid cleaning the filter would compromise my bacterial colony). Water parameters today after the scrub + 80% water change were NH4=0, NO2=0, NO3 just barely greater than 0. So I moved my (smaller) ryukin goldfish into the 20 gallon long. She is also acting lethargic, just resting at the bottom of the tank.

My Theories:
1) All those shrimp died in that tank - even though I removed each casualty before they could begin to rot and I've cleaned the media filter, the water, and the tank and fixtures, I didn't scrub the inside of the filter for fear of losing my biofilter - I only replaced the little cartridge. Could there be something in the filter that is fouling the water in some way that isn't shown on the tests I'm performing?

2) The LED strip on the top of that tank is really bright. It didn't seem to be a problem for the fantail who originally lived in that tank, but could it be stressing the tanks current inhabitants?

3) A 20 gallon long, while being enough water for a fancy goldfish, might not be enough vertical space for them? This doesn't really apply for the ryukin or the original fantail, but may have applied for the oranda.

If you are actually still reading this novel, you are a saint and I so appreciate you! Any thoughts or ideas would be greatly appreciated! Nothing I've tried seems to be helping.

Hi and welcome to the forum

Move the mystery snail in with the other one because there is something poisoning the 20g tank water. Don't worry about them breeding because they only produce a cluster of eggs every now and then and most of the baby snails don't survive. They are not a problem like other snails. And the snail is suffering so it needs clean water.

Do you have fish only buckets or do you use any bucket in the house when doing water changes?

What did you clean the tank out with before you set it up?

Was the aquarium new when you bought it, or was it second hand?
If it was second hand it could have been contaminated with anything that has left a residue behind and that is killing things.

What gravel/ substrate is in the tank, and is this new or second hand?

What ornaments. plants, objects are in the tank, and are these new or second hand?

Where do you get the water from that goes into the tank?
Do you use a water conditioner?

What is pH, general hardness (GH) & carbonate hardness (KH) of the tank water, tap water and other aquarium/s?
If the pH, GH & KH are the same in both tanks and the tap water then that would not be the issue.

What was the temperature getting up to when it was hot?

Is light unit resting on tank?
If it isn't poisoning (and I am pretty sure it is), there might be a slight electrical leakage into the tank from the light unit.

Please provide the numbers Colin asked for. I suspect we can rule out pH and hardness. My Cherries thrive in a pH of 7.8 with dGH 16 and dKH 20. They are quite sensitive to changes in water parameters so it is best to drip acclimate them, but I suspect if that was the problem they would all have died within days rather than some hanging on for a month.

Did you leave the heater on when you had the goldfish in there? The temperature swings shouldn't be a big deal but the small tank will heat up quicker during the day, and not cool down as much overnight if the heater is on (I'm assuming your goldfish normally live in an unheated tank).

What is the temerature difference between the 2 tanks in the morning and in the evening? Aside from the obvious, warm water holds less oxygen than cooler water. Chances are the overall temperature was lower when you originally had the fantail in there.

Finally was the filter ever in a tank that was treated with copper based medications or algaecides. That could be a death sentence for shrimps and snails (even if thoroughly cleaned).

I'm afraid I don't KNOW the answer either but that's a couple of things that sprang to mind.

Wow, thank you so much for the quick responses. I have officially moved everyone out of the 20 gallon tank - that mystery snail came out of its shell and started walking around the 30 gallon he was relocated to within 5 minutes of being introduced (yay, happy snail ). It seems pretty clear that something is poisoning the water in my 20 gallon.

I do have a whole set of fish-only buckets, sponges, cups, etc that have never touched anything except tank water. The 20 gallon was brand new when I got it - rinsed thoroughly with tap water before I set it up for animals. I put brand new, rinsed aquarium sand in it as substrate back when I originally set it up. I never use any products for cleaning my aquariums other than conditioned tap water and good, old-fashioned elbow grease.

There is a hollow plastic log and two plastic plants in the tank currently. They all came from previous tank setups of mine but were new to me when I originally got them. They were all cleaned as described above (fresh water and a good healthy scrub) and then completely dried before being stored.

I use local tap water in my tanks and condition it with Prime as it goes into the tank (I use a sink-powered syphon system like a python pump to change water).

My GH and KH are similar between my two tanks (the 20 gallon and a 30 gallon) and the tap water. Here are those numbers:
GH = 8 dGH for all 3 water sources
KH = 5 dKH for the tap water and the 30 gallon, KH = 4 dKH in that dastardly 20 gallon

I am showing some variation in pH. The tap water tests at pH = 7.6 while water in the 20 gallon is slightly more acidic - pH = 7.2 and water in the 30 gallon (my happy established tank) is sitting at pH = 7.0.

I can't be sure exactly how hot it got in the 20 gallon tank while my cherries were struggling in there - my home is cooled during the summer by a swamp cooler that only has an output vent into the living room. The 20 gallon is in the kitchen one room away and it definitely gets pretty warm in there (my mistake for putting a tank in there in the first place but...). When I was leaving for work at 6 am it was usually sitting at about 72 degrees and by the time I came home between 4-6 pm I was observing water temperatures of about 76 degrees. As I said, it is quite likely that the temperature got higher than that during the heat of the day. This was (in my opinion) my strongest theory about what was killing the shrimp. They were drip acclimated upon originally introducing them and I didn't have any deaths until after about the first week although they did seem generally to be having trouble molting. They'd start to turn a little white around the eyes but would just sit stationary for a long time and eventually keel over and die. That coincided with my finding way fewer molted shells in the tank.

I do keep a heater in all my tanks (even with my goldies) and do my best to keep my goldfish tanks at about 72 F. The weather was definitely cooler when the original fantail was in that tank (I hadn't thought of that so thanks!) so he wouldn't have experienced those wild temperature shifts. That being said, I suspect if my animals were objecting to tank temperature they'd be upset in the 30 gallon too (which they are not) because it is almost always within 1 degree of the 20 gallon tank (it has the same issue of not being directly in the room that gets the cool air).

The light sits on little feet that hold it up above the tank (see attached photo). I'd be pretty shocked (no pun intended) if it was able to leach electricity into the tank from where it's at.

The filter that I used on that 20 gallon tank was repurposed from my larger tank. I can't remember if it was on my 30 gallon when I treated for some illnesses last year - I definitely treated once for ich (using API's super ick cure) and another time for a hexamita infection (using API's general cure). I don't see anything about copper or heavy metals on the ich meds but I don't have the package for general cure anymore and if I remember correctly it was pretty nasty stuff - if my hang on back filter did coincide with that treatment it could certainly be an explanation for mass shrimp casualties.

So, next steps:
(1) Should I try scrubbing out that filter and accept having to re-cycle the tank?
(2) Should I invest in a new filter (a smaller one would be better on that tank anyway) and again accept my cycle being set back to square one?
(3) Do you think I need to ditch this substrate and replace it?

Everyone (2 orandas, 1 ryukin, and 2 mystery snails) seems happy in my 30 gallon tank but in the long run, someones gotta move out or I'll be doing water changes every other day...lol.

Thanks again for your thoughts and ideas!

Have you used the same substrate before in the other tank or is this the first time you have used that type/ brand of substrate?

The photo shows a piece of driftwood. Where did that come from and how long have you had it?

The plastic plants and plastic hollow log will be fine.

re: adding Prime to the tank as new water is pumped in. That did not cause the issue but you want to try and remove chlorine/ chloramine before it goes into the tank otherwise the fish could be exposed to high levels of chlorine/ chloramine and suffer gill damage/ burns. The best way to do this is fill a bucket with water, add dechlorinator (Prime) and then aerate the mixture for 30 minutes or so. This gives the water conditioner plenty of time to come in contact with all the chlorine/ chloramine molecules in the water and neutralise them before the water goes into the tank. It also allows the tap water to get normal gas levels back in it after being under pressure in the pipes.

I assume the gravel is acidic and dropping the pH and KH by using the carbonates in the water. This would explain the difference in tanks and tap water.

Your 30g should be fine for 3 goldfish and a couple of snails, at least for a while. Ryukins and Orandas only hit 4-5 inches long (body size not including tail). I wouldn't worry too much about them at this stage.

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I would remove the gravel and driftwood, then drain the tank and flush it out a few times before refilling it. Wait a few days then put the snail back in and see what happens. If the snail is fine then put a layer of gravel in a clean bucket and fill the bucket with water from the tank. Wait 24 hours then put the snail in the bucket with the gravel and see what happens. If the snail freaks out when in the bucket with the gravel, then the gravel is the problem.

Keep the driftwood out for the time being because that might be leaching something into the water.

Your small HOB filter should be fine, just wash the filter materials out in a bucket of water from the goldfish tank, and wash the filter case and motor with tap water. Then set it up on the goldfish tank for the time being.
If you have carbon in the HOB filter then throw it away and replace it with sponges if you can.

Do you have a local source of daphnia? They are great for testing water quality and don't cost anything. If they are still hopping about after 24 - 48 hours the water will be fine for shrimp and snails.

Its hard to say about the filter unless you know for sure that is the problem, and it doesn't explain why the goldfish had a hard time. If you do decide to change it a simple sponge filter will be perfectly adequate (and inexpensive). And cycling won't have to cause any stress on your goldies because you could just put into their tank and run side by side with their own filter for a few weeks.

pH differences shouldn't be a concern. Each tank is its own ecosystem and its normal for variance between tanks in the same house. When you test your tap water let it stand for a day before testing so the CO2 can gas out. Some suppliers also boost the pH tempoarily to prevent pipe corrosion.

Something that nobody has touched on: what plants are in there and where did you get them? The same goes for any wood or stones. Could it be as simple as pesticide or weed killer? Also is there anything else going on in that room that may have an effect, I'm thinking about things like electronic air fresheners or recent painting or decorating.

seangee said:

Something that nobody has touched on: what plants are in there and where did you get them? The same goes for any wood or stones. Could it be as simple as pesticide or weed killer? Also is there anything else going on in that room that may have an effect, I'm thinking about things like electronic air fresheners or recent painting or decorating.

Click to expand...

never looked at the pic, as Colin says it may still apply to the wood.

That "driftwood" is the hollow plastic log, I don't have any live plants, and the substrate is exactly the same as that in my 30 gallon (same brand and even same color). I can't think of any chemical additives in that room recently (we haven't painted and I'm very sensitive to fragrances/chemicals so we mostly just use vinegar and baking soda when cleaning). I'll remove the sand, drain, and rinse the tank today and clean the filter.

I'll have to ask the guys at my LFS about a local daphnia source, although, I am somewhat hesitant to attempt a shrimp tank in that room again. The summer temperature swings are so dramatic and thus far shrimp-keeping makes me feel like a murderer. Lol.

I'll keep you posted in a few days on how my snail does when I reintroduce her (definitely a her - she's currently doing the dirty deed with my other snail who is, in her presence, quite visibly a male). If she looks okay in the bare tank, I'll do the gravel bucket experiment.

Thanks so much to both of you for your help!

I don't think you will find live Daphnia in summer. It doesn't like hot weather and normally occurs in late autumn, winter and spring. If you have any ponds nearby you can check them for Daphnia but you might not find any until the weather cools down.

The plastic hollow wood might have been contaminated with something at the petshop or where you bought it from. Someone might have accidentally contaminated it. However, if it was rinsed well it should be fine.

Something else you can do with the gravel is set up 2 buckets with tap water in. Add a few inches of gravel to one bucket but leave the other one with just water. Check the pH and KH in both of these buckets several times throughout the day and do it for a few days. See if there is a change in water chemistry in the bucket with the gravel.

If the gravel is acidic and dropping the pH, then the shrimp would have been living on an acid substrate and getting alkaline water flowing above them. This would kill them. And if the gravel was quite acidic it would upset any snails that touch it. The snail has an operculum they can close up and this keeps the nasty stuff away from the actual snail hiding in its shell. This would allow the snail to live longer in the same conditions but it would spend most of its time closed up.