Issues with water quality

[Aquagirl123]

First of all thank you for letting me join this forum. I’m very new to the hobby. I have set up 2 29 gallon tanks. I went away for 2 weeks and was allowing them to cycle. One has a lid and the other doesn’t. When I got home, the one without the lid has a film covering the top of the water. Some suggestions were putting a paper towel over it and it would soak it up. Not working. Please advise!

[nabokovfan87]

On 11/13/2023 at 11:14 AM, Aquagirl123 said:

When I got home, the one without the lid has a film covering the top of the water. Some suggestions were putting a paper towel over it and it would soak it up. Not working. Please advise!

What is the filtration like in each tank? Photos do help if you wish to share them.

Sometimes the films we see in water can be due to chemicals or contamination, but sometimes it's just a more natural occurrence due to something like the substrate or filtration residues from production, proteins from food.

As for now, just do a good size water change and try to clean the walls of the tank off during that process. The goal being to rinse and remove any residue off of the walls and add fresh water. 

An air stone and water movement would help to keep the residue in the water column long term, but sometimes they can be very persistent and stay at the top of the waters surface.  I wouldn't be concerned at all until you have the tank setup for months and are still seeing that same film on the waters surface, indicating it's from food or the fish themselves.

[Aquagirl123]

I have no fish yet thank goodness. I’m concerned about the BB if I do a substantial water change. I will add some aeration though.

[Rube_Goldfish]

On 11/13/2023 at 4:19 PM, Aquagirl123 said:

I have no fish yet thank goodness. I’m concerned about the BB if I do a substantial water change. I will add some aeration though.

The beneficial bacteria live almost exclusively on surfaces inside the tank and filter, not in the water column. As long as those surfaces stay wet, and as long as the parameters of the new water are roughly similar to the old water, water changes can't really affect the beneficial bacteria.*

* The exception to this would be if you're still cycling; then a water change might slow the growth of the BB colony by reducing the amount of ammonia and/or nitrite in the water column, but it wouldn't hurt them in the mid- to long-term, and you can get more ammonia back in the tank post-water change pretty easily.

[nabokovfan87]

On 11/13/2023 at 1:19 PM, Aquagirl123 said:

I have no fish yet thank goodness. I’m concerned about the BB if I do a substantial water change. I will add some aeration though.

As mentioned above, you're safe to do water changes. Normally when you're dosing bacteria starter from a bottle you would just add it after the water change is completed. Wait 24 hours before your next water change, but apart from that you're good to go.

In a situation like this, it's not a major issue to do a one off water change. It's really common if you're using a soil substrate.

Looking at the photo, I don't see anything to really be concerned with. Monitor it and keep an eye on things. It all looks good.

The sort of slime you'd want to avoid would be the rainbow colors at the water surface. Those reduce gas exchange.

Here's two examples...

The first one is just from stagnant water and would be removed by using a fine net and adding surface agitation.

The next one is more of the oil and that's where people would remove it by using a skimmer or water changes.

[Aquagirl123]

Thank you so much for the information. I’ll do a water change tomorrow and get some aerators.

[Rube_Goldfish]

On 11/13/2023 at 6:05 PM, Aquagirl123 said:

Thank you so much for the information. I’ll do a water change tomorrow and get some aerators.

As @nabokovfan87 said, surface agitation is probably your best bet, long term, of getting rid of it and preventing recurrence. But you should also know that it can be pretty common, especially in new, still-stabilizing tanks. And in the short term, you can use a cup or a water bottle to skim it off, like you see at about the 0:40 mark of this video: