Donated Tank with Florida Gar

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AquaticsAmber

Feeder Fish
May 28, 2026
3
0
1
44
Houston
Have you tested your water?
Yes
If yes, what is your ammonia?
2-4ppm
If yes, what is your nitrite?
0.25ppm
If yes, what is your nitrate?
n/a
If I did not test my water...
  1. ...I recognize that I will likely be asked to do a test, and that water tests are critical for solving freshwater health problems.
Do you do water changes?
Yes
What percentage of water do you change?
51-60%
How frequently do you change your water?
Every week
If I do not change my water...
  1. ...I recognize that I will likely be recommended to do a water change, and water changes are critical for preventing future freshwater health problems.
Hello all,
Typing on phone so I apologies for errors. I'm an aquatic science teacher, but my background is mostly field and mostly marine so I have limited experience with fresh water tanks. On Tuesday, a local family donated a 75 gallon tank with it's occupants to our program. They had apparently had it for a little over a year with the following occupants: 4 red eared sliders of various sizes, 1 pleco, 1 smallish (<12inches) Florida Gar. Unfortunately, the tank arrived with a brand new UV filter, but not the original filter that had cycled with the tank, and the tank is also bare bottomed, so there's no substrate. As you might guess, when I ran chemistry today (Thursday) the ammonia was 2-4ppm and the nitrite was at 0.25. Like I said, not super experienced with freshwater tanks, so not sure how much trouble I'm in... The other bad news is because of summer, I won't have access to the building again until Monday. I did a 50% water change today before I left and added a whole bunch of quickstart because I had it, but I'm not feeling too great about what I might find on Monday.

Looking for advice on what I can reasonably do to keep this tank healthy over the summer given limited resources and limited access. I have a few HOB filters that I can add, I feel like the one little UV filter likely isn't actually enough filtration given the load? Honestly feel the tank is overstocked, but not much I can do about that in the immediate future. I do have 2 cycled 20gallons, but they're currently occupied with an axolotl and 5 pea puffers respectively, but I could at least grab some filter media from them if needed. I didn't feed anything today because I didn't want to add to the bioload. There were 5-6 feeder goldfish on Tuesday but they were all gone by today. They also brought a whole bunch of turtle, fish, and algae pellets, but said they regularly fed the goldfish as well.

My original plan was to come up to campus about once a week (it's a 30-45 minute drive each way for me). I'll obviously come up more often if the tank needs regular water changes, but if I can get it cycled back up will that once a week schedule still work? About how often/ how many feeder goldfish should I plan on adding? Thank you for any advice, feeling a little over my head...
 
add as much of the cycled filter media as you can from the 2 x 20’s for certain. What type of filter is in the 75gal?
The turtles and the pleco will be fine, though 4 turtles seems a lot as well 🤔
If the gar survives the weekend I would rehome it asap and in the meantime add 1tbsp/5gal of pure salt to prevent nitrite poisoning. A 75 gal is in now way big enough to house that fish 🤙🏼
 
add as much of the cycled filter media as you can from the 2 x 20’s for certain. What type of filter is in the 75gal?
The turtles and the pleco will be fine, though 4 turtles seems a lot as well 🤔
If the gar survives the weekend I would rehome it asap and in the meantime add 1tbsp/5gal of pure salt to prevent nitrite poisoning. A 75 gal is in now way big enough to house that fish 🤙🏼
The only filter in it right now is the submersible UV filter. It says it has a sponge filter inside it for biological filtration, but no mention of flow rate or any other information. It's made in china, not any brand I recognize, and the box and insert were pretty useless. I'll put two HOBs on it monday and trade out the uncycled sponges in those with the ones from the 2 20s.

Definitely will plan to rehome the gar, just not sure how quickly I can make that happen.

For the salt, is that marine salt mix? I have saltwater tanks as well so I have plenty, but want to make sure I'm using the right stuff.
 
Actually, just thinking of it now, but if I'm adding salt anyways, I have a fully cycled 55 gallon saltwater tank sitting empty right now that I could pull the filters off of. Would they work or would moving them from saltwater to freshwater crash them?
 
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