Pleco fry and Hydra

toddnbecka · Post by **toddnbecka** » 28 May 2006, 09:26

Are hydra capable of killing .5-.75" pleco fry? I have seen them decimate cichlid fry that weren't free-swimming yet. I had 7 in my 10 gallon planted cherry shrimp tank, all died in less than 2 weeks. They were active, getting plenty to eat, then suddenly died off within a few days. I noticed an abundance of hydra in the tank, and wondered if that could have been the cause?

Post by **Janne** » 28 May 2006, 17:18

No, they are harmless to youngsters...maybe they can do some damage before they have consumed their yolksac but not after they are free swimming. But fry and youngsters are sensitive at that size you mention if the substrate not are regulary cleaned, the bacteria level in the substrate produce a lot of nitrogen products as nitrit and nitrat and the oxygen level is much lower at the bottom where you usually find your pleco's, small fry or youngsters with their small bodys gets easily affected even in very low levels. It's important to keep the tank very clean and regulary (every week) clean the substrate to avoid high levels of both bacteria and nitrogen in and near the bottom, change water often and dont be afraid to put a small powerhead in the tank which will increase the oxygen level in the whole tank...even near the bottom.

Janne

toddnbecka · Post by **toddnbecka** » 28 May 2006, 19:21

The tank is filtered by a 100GPH hob filter, as well as an air-driven sponge filter. Plenty of plants, and weekly partials. Cherry shrimp are very sensitive to nitrates, and have been thriving w/no losses, (other than from hydra, which I have been removing w/an airline siphon whenever I find them, considerably reducing their numbers).
The substrate has been somewhat neglected, though it is occupied by MTS, so food doesn't linger long enough to decay. I thought that if the shrimp were doing alright, so would the pleco fry. Obviously, I was wrong somewhere in that belief.

Post by **Janne** » 28 May 2006, 20:14

The problem with very small pleco fry or youngster is that they are living at the bottom constantly more or less...their mouth and gills are just one mm or less from the surface of the substrate where the bacteria lives and consume the oxygen and release the carbon dioxide, the same with your MTS...a few is good but not many, both also produce nitrogen.
So, the substrate is important even if your water parameters seams to be fine.

Janne