NO gravel = constant disease?

[salstyles]

Have you tested your water?

No

If I did not test my water...

...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?

21-30%

How frequently do you change your water?

Every week

If I do not change my water...

...I recognize that I will likely be recommended to do a water change, and water changes are critical for preventing future freshwater health problems.

One of my tanks with molly kept getting fit rot and velvet! No matter how heavy the filtration! and water changes!

I realized that tank had hardly any gravel do you think that is what it was? I added sand in today. I never had a break out in sickness with tanks that have gravel.

That one tank just had soo many problems. I cant believe it took this long to realize it was the gravel. The only fish that were not effected were the archerfish and the giant danio.

Nitrate spikes does not seem to effect danio and archerfish seem to do really well for some reason with our insane hard tap water.

 

[phreeflow]

That’s an interesting observation and one I wondered about. I’ve never had issues with bare bottom and large/adult fish and they actually do better. However, I have had issues with fry.

Many of my fry end up getting bacterial infections in bare bottom tanks even with plenty of filtration and siphoned often. I’ve added snails, dwarf cories, shrimp, and bristlenose to help clean up the bottom but still end up with belly sliders and whirlers.

I now only raise fry in tanks with a fine layer of sand and they do much better. Not sure about your mollies though…could be bad genetics or many are farmed in brackish farms and may have trouble in full fresh.

 

[salstyles]

I think single fish like a wet pet are fine in bare bottom like arowanna but when you have a group so many issues happen.

 

[jjohnwm]

As long as the fish in question don't normally burrow or sift the substrate for food, then there's no way that a bare bottom tank should be causing problems. Bare bottoms are definitely easier to keep clean; the lack of substrate means that there is somewhat less surface area for beneficial bacteria, but if the tank is sufficiently filtered that should be a non-issue.

I like the look of a substrate, and many fish appreciate the chances for digging, sifting, etc. so most of my tanks have a substrate. My Jelly Cat, who produces thumb-sized poops, is on hard tile to facilitate cleaning them up; same with my big Axolotl. And of course all my outdoor stock tanks are bare bottom, aside from a natural accumulation of bottom sediment, which in turn fosters the population of microfauna that serve as food for fry.

Mollies like hard, alkaline water. If you have them crowded, a 30% weekly water change may not be enough to prevent nitrate build-up and gradual pH drop. I'm not typically one to be obsessively testing water parameters unless a problem seems to be cropping up...but in this case a problem is cropping up! A chronic ongoing issue like this demands monitoring your water conditions; start testing.

 

[duanes]

If, you live in an area witth regular power outages, a lack of substrate came be problematic,.
Substrate can be a make or brake DO, and if an external filter is wimpy, or goes out, depending on stocking, and if a lack of decore is used.
DO can easily drop to low levels. (expecially for rheophiles, like Geos, Tomcichlla, or other high DO requirig species)
Substrate can hold millions of aerobic bacteria.
Because I live in a regular power outage area, and keep rheophilies, always keep plenty of substrate, and also keep battery pumps at the ready,