High Nitrates - 87 guppies in a 20gal - What the heck!
I want to start out with - I did not put 87 guppies in a 20 gal tank, but I have adopted this tank as is. Yikes.
This lady was moving across the country and she couldn't take her fish with her. She told me she had a 20gal with some guppies and wanted to know if I wanted it. Well, of course I could take this burden off of her hands! lol
I get there and her 20 gal long has a TON of guppies!!! I couldn't imagine how she had them thriving so well! They are reproducing and they all looked healthy besides some tail nipping. Then she tells me that she doesn't really do water changes - yikes! She sometimes takes water from the top, but mostly just adding water when the level got low. No under gravel filtration, no airstone and she used a HoB filter (not sure what kind because she wanted to keep it). She has these chunky river rocks instead of gravel. No algae issues either!
I get it home with about 75% of the water. I start testing the water - no ammonia or nitrites. I'm shocked! But then the nitrates were really bad - 100-130ppm! So I start working at 25% water changes everyday. And every time I used the substrate vacuum, the tons of debris would fly really bad. So it was obvious that she didn't clean the bottom much at all. I did have issues with guppy fry getting sucked up because they would hide in between the rocks. Luckily, I siphoned into a bucket and was able to add them back. I also added some low light plants that I took from my 55gal planted tank in hopes that it would use up some of the nitrates. I also added a nitrate-absorbing material that could be added to my filter.
I did this every day for 2 weeks, which was very time consuming dealing with the fry. I tested the nitrates, but it wasn't budging. Tap water nitrates was about 10ppm. So why on earth are the nitrates not dropping? It had to be the massive amount of crap under these rocks, right? So I ended up spending 5 hours breaking down this tank, cleaning and re-assembling.
Netting up all of these guppies, including the fry, came to 87 guppies!!!! OMG! And I had to slowly grab the rocks a handful at a time to remove, because the fry had created a tunnel of hiding spots in them. Exhausting!
The debris left in the bottom was a disgusting layer. After cleaning and changing out 50% of the water, I finally got to 40ppm on nitrates! I was super thrilled with this. The large water change caused a mini-cycle for 24 hrs, but cleared up quickly.
The next day, my nitrates rose to 60ppm. What the heck! Still no ammonia. And I'm still surprised that I don't have any algae issues. So how can I keep the nitrates down with a MAJORLY HUGE bio-load? I have a HoB filter on this tank and because of the location of the tank in my house, I won't be able to change to a canister (no spot under the tank for it to be).
I would LOVE to take half of these guppies out and add to my 55gal, which has a very low bio-load and heavily planted. But I have an a-hole....I mean a red tail shark in the 55gal, and he loves to chase everything that moves.
Is it possible to keep this tank with this many guppies or do I need to unload a lot of guppies on craigslist to random people? Any other way I can lower the nitrates?